NSTAR 2017
The 11th International Workshop on the Physics of Excited
Nucleons

August 20 – 23, 2017at the University of South Carolina, Columbia, SC

Organizers:
R. Gothe (Chair), Y. Ilieva, V. Mokeev, E. Santopinto, and S. Strauch

NSTAR 2017 — Book of Abstracts

List of Speakers
1. Adhikari, Shankar, “Measurement of polarization observables for Lambda in the reaction γp →K + Λ”, Parallel Session A3 (DMSB 124) on Tuesday, August 22, 2017, 17:10.
2. Akbar, Zulkaida , “Photoproduction of ω Mesons using CLAS at Jeﬀerson Laboratory ”, Parallel
Session A3 (DMSB 124) on Tuesday, August 22, 2017, 16:30.
3. Angelini, Giovanni, “CLAS12 RICH: New hybrid geometry for strangeness studies.”, Parallel
Session B5 (DMSB 125) on Wednesday, August 23, 2017, 11:40.
4. Bashir, Adnan, “Structure of the Orbital Excited N* from SDE”, Parallel Session B4 (DMSB 125)
on Wednesday, August 23, 2017, 08:30.
5. Bernauer, Jan, “Two-Photon-Exchange: Future experimental prospects”, Parallel Session C3(DMSB 126) on Tuesday, August 22, 2017, 16:50.
6. Blunden, Peter, “Overview of recent theoretical work on two-photon exchange”, Parallel Session
C3 (DMSB 126) on Tuesday, August 22, 2017, 16:00.
7. Briceno, Raul, “Resonance properties via lattice QCD”, Parallel Session B1 (DMSB 125) on Sunday, August 20, 2017, 13:30.
8. Brodsky, Stanley J., “Supersymmetric features of hadron physics and other novel properties of
QCD from Light-Front Holography and Superconformal Quantum Mechanics ”, General Session
P5 (DMSB 123) on Tuesday, August 22, 2017, 10:00.
9. Buchmann, Alfons, “Electromagnetic multipole moments of baryons”, Parallel Session D3(DMSB 122) on Tuesday, August 22, 2017, 17:10.
10. Bulava, John, “Hadron scattering amplitudes from lattice QCD with controlled errors”, Parallel
Session B1 (DMSB 125) on Sunday, August 20, 2017, 14:00.
11. Burkert, Volker, “A Light Front Relativistic Quark Model with Running Quark Mass”, Parallel
Session D3 (DMSB 122) on Tuesday, August 22, 2017, 16:30.
Burkert, Volker, “N* Experiments and their Impact on Strong QCD Physics”, General Session
P1 (DMSB 123) on Sunday, August 20, 2017, 09:00.
12. Cao, Tongtong, “Determination of the Polarization Observables Cx , Cz , and Py for the Quasi-Free−→→
Mechanism in the reaction −γ d → K + Λ n”, Parallel Session A4 (DMSB 124) on Wednesday,
August 23, 2017, 10:00.
13. Carman, Daniel, “CLAS N* Excitation Results from Pion and Kaon Electroproduction”, General
Session P7 (DMSB 123) on Wednesday, August 23, 2017, 15:30.
14. Cole, Philip, “Bridging Time-Like and Space-Like N* Form Factors”, Parallel Session C5 (DMSB
126) on Wednesday, August 23, 2017, 10:50.
15. Crede, Volker, “Understanding the Spectrum of Excited Nucleons using CLAS at Jeﬀerson Lab”,
General Session P5 (DMSB 123) on Tuesday, August 22, 2017, 09:00.
16. D’Angelo, Annalisa, “Hybrid Baryon Search at CLAS12”, General Session P4 (DMSB 123) on
Monday, August 21, 2017, 12:00.
1

NSTAR 2017 — Book of Abstracts
17. Davoudi, Zohreh, “Beyond nucleon properties from lattice QCD”, Parallel Session B2 (DMSB
125) on Tuesday, August 22, 2017, 14:30.
18. Deur, Alexandre, “The QCD running coupling at all scales and the connection between the proton
mass and ΛM S ”, Parallel Session B4 (DMSB 125) on Wednesday, August 23, 2017, 09:40.
19. Doering, Michael, “Developments of the Julich-Bonn Dynamical Coupled-Channel Analysis”,
General Session P5 (DMSB 123) on Tuesday, August 22, 2017, 08:30.
20. Eichmann, Gernot, “Baryon structure and reaction mechanisms from Dyson-Schwinger equations”, General Session P4 (DMSB 123) on Monday, August 21, 2017, 11:30.
21. Elouadrhiri, Latifa, “Conﬁnement in N* and DIS Physics”, Parallel Session C1 (DMSB 126) on
Sunday, August 20, 2017, 13:30.
22. Fedotov, Gleb, “New results on γv p → p0 π + π − cross sections in the resonance region with
CLAS”, Parallel Session A5 (DMSB 124) on Wednesday, August 23, 2017, 12:20.
23. Fersch, Robert, “Measurements of the Nucleon Spin-Structure Functions in and above the Resonance Region from the Hall-B EG1 experiment at Jeﬀerson Laboratory”, Parallel Session A1(DMSB 124) on Sunday, August 20, 2017, 14:20.
24. García-Tecocoatzi, Hugo, “Baryon masses and strangeness suppression in the Unquenched Quark
model”, Parallel Session D3 (DMSB 122) on Tuesday, August 22, 2017, 16:50.
25. Girod, Francois-Xavier, “Unraveling conﬁnement forces with DVCS”, Parallel Session C1(DMSB 126) on Sunday, August 20, 2017, 14:00.
26. Gleason, Colin, “Determination of the Hyperon Induced Polarization and Polarization–Transfer
Coeﬃcients for Quasi-Free Hyperon Photoproduction oﬀ the Bound Neutron”, Parallel Session
A2 (DMSB 124) on Tuesday, August 22, 2017, 14:50.
27. Grames, Joseph, “Polarized Positron Beam R&D at Jeﬀerson Lab”, Parallel Session C3 (DMSB
126) on Tuesday, August 22, 2017, 17:10.
28. Hagelstein, Franziska, “The Role of the ∆(1232)-Resonance in the (Muonic) Hydrogen Spectrum”, Parallel Session C4 (DMSB 126) on Wednesday, August 23, 2017, 09:20.
29. Hansen, Maxwell, “Total decay and transition rates from LQCD”, Parallel Session B1 (DMSB
125) on Sunday, August 20, 2017, 14:20.
30. Hiller Blin, Astrid, “Relating CP-violating decays to the neutron EDM”, Parallel Session B3(DMSB 125) on Tuesday, August 22, 2017, 17:10.
Hiller Blin, Astrid, “Peripheral transverse densities of the baryon octet from ChPT and dispersion
analysis”, Parallel Session C1 (DMSB 126) on Sunday, August 20, 2017, 14:20.
Hiller Blin, Astrid, “Studying the Pc(4450) resonance in J/psi photoproduction oﬀ protons”, Parallel Session D2 (DMSB 122) on Tuesday, August 22, 2017, 14:50.
31. Hollis, Gary, “Fermi-unsmearing: A Monte Carlo method to correct for Fermi-motion of a target
nucleon.”, Parallel Session A4 (DMSB 124) on Wednesday, August 23, 2017, 09:40.
32. Huang, Fei, “Nucleon resonances in γp→K∗+Λ”, Parallel Session B3 (DMSB 125) on Tuesday,
August 22, 2017, 17:30.

2

NSTAR 2017 — Book of Abstracts
33. Ireland, Dave, “Evaluating Polarization Data”, Parallel Session B5 (DMSB 125) on Wednesday,
August 23, 2017, 11:20.
34. Jiang, Hao, “Polarization Observables T and F in the p(γ, π 0 )p Reaction”, Parallel Session A3(DMSB 124) on Tuesday, August 22, 2017, 17:50.
35. Jones, Mark, “Virtual Compton Scattering measurements in Hall C at JLab”, Parallel Session C4(DMSB 126) on Wednesday, August 23, 2017, 10:00.
36. Jung, Ju-Hyun, “Constituent-quark model with pionic contributions: electromagnetic N → ∆transition”, Parallel Session D3 (DMSB 122) on Tuesday, August 22, 2017, 17:30.
37. Kamano, Hiroyuki, “Electromagnetic N* Transition Form Factors in the ANL-Osaka Dynamical
Coupled-Channels Approach”, General Session P3 (DMSB 123) on Monday, August 21, 2017,
10:00.
38. Kohl, Michael, “Experimental Advances in Two-Photon Contributions to Lepton-Proton Scattering”, Parallel Session C2 (DMSB 126) on Tuesday, August 22, 2017, 14:00.
39. Kohri, Hideki, “Photoproduction of π − ∆++ , π + ∆0 , and π + n on the proton at Eγ = 1.5 − 3.0
GeV at LEPS/SPring-8”, Parallel Session B3 (DMSB 125) on Tuesday, August 22, 2017, 16:50.
40. Koshchii, Oleksandr, “Lepton mass eﬀects in two-photon exchange theory”, Parallel Session C2(DMSB 126) on Tuesday, August 22, 2017, 14:50.
41. Koutsou, Giannis, “Nucleon and Delta structure results from lattice QCD”, Parallel Session C4(DMSB 126) on Wednesday, August 23, 2017, 09:00.
42. Lebed, Richard, “Constituent Counting Rules and Exotic Hadrons”, Parallel Session D2 (DMSB
122) on Tuesday, August 22, 2017, 15:10.
43. Leskovec, Luka, “A lattice QCD study of pion-nucleon scattering in the Roper channel”, Parallel
Session B2 (DMSB 125) on Tuesday, August 22, 2017, 14:50.
44. Leupold, Stefan, “Hyperon-photon physics”, Parallel Session C5 (DMSB 126) on Wednesday,
August 23, 2017, 11:40.
45. Lu, Haiyun, “Beam-Target Asymmetry for γn(p) → π − p(p) in N ∗ Resonance Region”, Parallel
Session A2 (DMSB 124) on Tuesday, August 22, 2017, 15:10.
46. Mai, Maxim, “Status of the Lambda(1405)”, General Session P3 (DMSB 123) on Monday, August21, 2017, 09:00.
47. Markov, Nikolay, “Exclusive π 0 electroproduction in the resonance region.”, Parallel Session A5(DMSB 124) on Wednesday, August 23, 2017, 11:20.
48. Mathieu, Vincent, “Analyticity Constraints for the Baryon Spectrum”, Parallel Session D2(DMSB 122) on Tuesday, August 22, 2017, 14:00.
49. Mattione, Paul, “γn → pπ − Cross Section Measurement at CLAS”, Parallel Session A2 (DMSB
124) on Tuesday, August 22, 2017, 14:00.
50. McKeown, Bob, “Future Facilities and QCD Physics”, General Session P2 (DMSB 123) on Sunday, August 20, 2017, 11:30.

3

NSTAR 2017 — Book of Abstracts
51. Melnitchouk, Wally, “Duality between resonances and parton physics”, Parallel Session A1(DMSB 124) on Sunday, August 20, 2017, 13:30.
52. Mokeev, Victor, “Nucleon Resonance Structure from Exclusive Meson Electroproduction with
CLAS”, General Session P2 (DMSB 123) on Sunday, August 20, 2017, 11:00.
53. Myhrer, Fred, “Lepton bremsstrahlung at low energies”, Parallel Session C3 (DMSB 126) on
Tuesday, August 22, 2017, 17:30.
54. Nakamura, Satoshi, “Photo- and Electroexcitation of Bound Neutrons and Protons”, Parallel Session B3 (DMSB 125) on Tuesday, August 22, 2017, 16:00.
55. Net, Lelia, “Polarization observables in double charged pion photo-production with circularly polarized photons oﬀ transversely polarized protons”, Parallel Session A3 (DMSB 124) on Tuesday,
August 22, 2017, 17:30.
56. Niculescu, Ioana , “Quark Hadron Duality in Unpolarized Structure Functions”, Parallel Session
A1 (DMSB 124) on Sunday, August 20, 2017, 14:00.
57. Nys, Jannes, “Finite-Energy Sum Rules in Eta Photoproduction oﬀ the Nucleon”, Parallel Session
D2 (DMSB 122) on Tuesday, August 22, 2017, 14:30.
58. Oset, Eulogio, “Chiral Unitary and New Developments in the Baryon Sector”, General Session P6(DMSB 123) on Tuesday, August 22, 2017, 11:00.
59. Paolone, Michael, “The VCS-Δ experiment at MAMI”, Parallel Session C4 (DMSB 126) on
Wednesday, August 23, 2017, 09:40.
60. Park, Kijun, “Extracting Resonance Parameters from Exclusive Electroproduction oﬀ Protons at
CLAS”, Parallel Session A5 (DMSB 124) on Wednesday, August 23, 2017, 10:50.
61. Pasyuk, Eugene, “Advances in N* spectroscopy from Exclusive Photoproduction at CLAS”, Parallel Session A3 (DMSB 124) on Tuesday, August 22, 2017, 16:00.
62. Phelps, Evan, “Response Functions from Exclusive Measurements of ω Meson Electroproduction
oﬀ the Proton”, Parallel Session A5 (DMSB 124) on Wednesday, August 23, 2017, 11:40.
63. Pisarski, Robert, “When are mesons eigenstates of SU(3) versus that of ﬂavor?”, Parallel Session
C1 (DMSB 126) on Sunday, August 20, 2017, 14:40.
64. Ramalho, Gilberto, “N* Form Factors based on a Covariant Quark Model”, Parallel Session D3(DMSB 122) on Tuesday, August 22, 2017, 16:00.
65. Ramstein, Béatrice, “Studying time-like electromagnetic baryonic transitions with HADES in
π-N reactions”, Parallel Session C5 (DMSB 126) on Wednesday, August 23, 2017, 11:20.
Ramstein, Béatrice, “Time-Like Baryon Transitions in Hadroproduction”, General Session P7(DMSB 123) on Wednesday, August 23, 2017, 15:00.
66. Roberts, Craig, “N* Structure: A Window on Strong QCD”, General Session P1 (DMSB 123) on
Sunday, August 20, 2017, 09:30.
67. Rodríguez-Quintero, José, “A process-independent QCD eﬀective charge: a main ingredient fora further computation of nucleon-to-resonances transitions”, Parallel Session B4 (DMSB 125) on
Wednesday, August 23, 2017, 09:00.

4

NSTAR 2017 — Book of Abstracts
68. Ryckebusch, Jan, “Resonance Parameters from Strangeness Photo- and Electroproduction”, General Session P7 (DMSB 123) on Wednesday, August 23, 2017, 14:00.
69. Sadasivan, Daniel, “Disentanglement of Electromagnetic Baryon Properties”, Parallel Session B4(DMSB 125) on Wednesday, August 23, 2017, 10:00.
70. Sandorﬁ, Andrew, “Spin Asymmetries and Helicity Amplitudes from Pion Production from Polarized Neutrons at Jeﬀerson Lab”, General Session P3 (DMSB 123) on Monday, August 21, 2017,08:30.
71. Santopinto, Elena, “N* Structure from Constituent Quark Models”, General Session P8 (DMSB
123) on Wednesday, August 23, 2017, 17:00.
72. Sato, Toru, “Quark-hadron duality in parity-violating electroweak reactions”, Parallel Session A1(DMSB 124) on Sunday, August 20, 2017, 14:40.
Sato, Toru, “Exclusive Meson Electroproduction oﬀ Bound Nucleons”, General Session P8(DMSB 123) on Wednesday, August 23, 2017, 16:30.
73. Schmieden, Hartmut, “First Results from the BGO-OD Experiment at ELSA”, Parallel Session
C5 (DMSB 126) on Wednesday, August 23, 2017, 12:20.
74. Segovia, Jorge, “Valence-quark structure in nucleon resonances from DSEs”, General Session P6(DMSB 123) on Tuesday, August 22, 2017, 12:00.
75. Shah, Zalak, “Mass spectra of singly beauty Ω−b baryon”, Parallel Session D3 (DMSB 122) on
Tuesday, August 22, 2017, 17:50.
76. Shanahan, Phiala, “Gluon structure of hadrons”, Parallel Session B1 (DMSB 125) on Sunday,
August 20, 2017, 14:40.
77. Skorodumina, Iuliia, “Investigation of Exclusive π + π − Electroproduction oﬀ the Bound Proton in
Deuterium in the Resonance Region with CLAS”, Parallel Session A4 (DMSB 124) on Wednesday,
August 23, 2017, 09:20.
78. Sokhoyan, Vahe, “N* Photoexcitation Results from Mainz”, General Session P5 (DMSB 123) on
Tuesday, August 22, 2017, 09:30.
79. Sparveris, Nikos, “N to Δ transition: recent results and prospects”, Parallel Session C4 (DMSB
126) on Wednesday, August 23, 2017, 08:30.
80. Strakovsky, Igor, “Exclusive Meson Photoproduction oﬀ Bound Nucleons”, Parallel Session B5(DMSB 125) on Wednesday, August 23, 2017, 10:50.
81. Strauch, Steﬀen, “Baryons in Medium”, General Session P8 (DMSB 123) on Wednesday, August23, 2017, 17:30.
82. Svarc, Alfred, “From Experimental Data to Pole Parameters in a Model Independent Way (Angular
Dependent Phase Rotations and L+P method)”, General Session P3 (DMSB 123) on Monday,
August 21, 2017, 09:30.
83. Tandy, Peter, “Aspects of Nucleon Parton Structure from a DSE Implementation of QCD”, Parallel
Session B4 (DMSB 125) on Wednesday, August 23, 2017, 09:20.
84. Thiel, Annika, “N* Photoexcitation Results from Bonn”, General Session P4 (DMSB 123) on
Monday, August 21, 2017, 11:00.
5

NSTAR 2017 — Book of Abstracts
85. Tian, Ye, “Exclusive π − Electroproduction oﬀ the Neutron in Deuterium in the Resonance Region”, Parallel Session A4 (DMSB 124) on Wednesday, August 23, 2017, 08:30.
86. Tiator, Lothar, “The MAID Legacy and Future”, General Session P1 (DMSB 123) on Sunday,
August 20, 2017, 10:00.
87. Tomalak, Oleksandr, “Two-photon exchange correction in elastic lepton-proton scattering. Dispersive and model calculations”, Parallel Session C2 (DMSB 126) on Tuesday, August 22, 2017,15:10.
88. Tomasi-Gustafsson, Egle, “Two-photon exchange: myth and history”, Parallel Session C3(DMSB 126) on Tuesday, August 22, 2017, 16:30.
89. Trivedi, Arjun, “Measurement of New Observables from the π + π − p Electroproduction oﬀ theProton”, Parallel Session A5 (DMSB 124) on Wednesday, August 23, 2017, 12:00.
90. Walford, Natalie, “Polarization Observables in Meson Photoproduction with the Crystal
Ball/TAPS at MAMI”, Parallel Session A2 (DMSB 124) on Tuesday, August 22, 2017, 14:30.
Walford, Natalie, “Polarization Observables in γp → K + + Λ and K + + Σ0 Using Circularly Polarized Photons on a Polarized Frozen Spin Target”, Parallel Session A3 (DMSB 124) on Tuesday,
August 22, 2017, 16:50.
Walford, Natalie, “Photoproduction of π 0 π ± Pairs oﬀ Nucleons”, Parallel Session B5 (DMSB
125) on Wednesday, August 23, 2017, 12:00.
91. Wilson, David, “An a0 resonance from lattice QCD”, Parallel Session B2 (DMSB 125) on Tuesday,
August 22, 2017, 14:00.
92. Wu, Jiajun, “Nucleon Excited States from Lattice QCD and Hamiltonian Eﬀective Field Theory”,
General Session P7 (DMSB 123) on Wednesday, August 23, 2017, 14:30.
93. Xie, Ju-Jun, “Nucleon N(2120) resonance in φp and KΛ(1520) photon production”, Parallel Session B3 (DMSB 125) on Tuesday, August 22, 2017, 16:30.
94. Yurov, Mikhail, “Two-photon exchange contribution to elastic electron-proton scattering”, Parallel
Session C2 (DMSB 126) on Tuesday, August 22, 2017, 14:30.
95. Zhang, Jixie, “Exclusive π − electroproduction from the neutron in the resonance region”, Parallel
Session A4 (DMSB 124) on Wednesday, August 23, 2017, 09:00.
96. Zou, Bing-Song, “N* Production from e+ e− Annihilation”, General Session P6 (DMSB 123) on
Tuesday, August 22, 2017, 11:30.
97. Zétényi, Miklós, “Polarization and dilepton anisotropy in pion-nucleon collisions”, Parallel Session C5 (DMSB 126) on Wednesday, August 23, 2017, 12:00.

6

NSTAR 2017 — Book of Abstracts

Sunday, August 20, 2017

ProgramSaturday, August 19, 2017

Registration
Time: Saturday, August 19, 2017, 18:00 – 19:30
Room: Sonoco Pavilion

Opening Reception
Time: Saturday, August 19, 2017, 18:00 – 20:00
Room: Sonoco Pavilion

Sunday, August 20, 2017

Registration
Time: Sunday, August 20, 2017, 07:30 – 09:00
Room: Lobby near DMSB 123

Opening / Welcome / Introduction
Time: Sunday, August 20, 2017, 08:30 – 09:00
Room: DMSB 123

General Session P1
Time: Sunday, August 20, 2017, 09:00 – 10:30
Room: DMSB 123
Chair: Steﬀen Strauch
N* Experiments and their Impact on Strong QCD Physics
Volker Burkert, Jeﬀerson Laboratory
Strong QCD is our theoretical tool to come to a full understanding of the physics of conﬁnement, dynamical mass creation, and the breaking of chiral symmetry. With the right experimental and theoretical tools,
the study of the structure of the nucleon and its energy spectrum can provide a tremendous amount ofknowledge of the degrees of freedom underlying the excitation of nucleons. Nathan Isgur, in his last public talk at the NSTAR 2000 conference at Jeﬀerson Lab, entitled “Why N*’s are important?”, gave three
answers: (1) “Nucleons are the stuﬀ of which our world is made. As such they must be at the center ofany discussion of why the world we actually experience has the character it does”. (2) “Nucleons are the7

09:00
DMSB 123NSTAR 2017 — Book of Abstracts

Sunday, August 20, 2017

simplest system in which the quintessentially non-abelian character of QCD is manifest.” (3) “Baryons,
while relatively simple, are suﬃciently complex to reveal physics hidden from us in the mesons.” In
the opening talk of this conference I will emphasize the importance of precision measurements of many
diﬀerent ﬁnal meson states, and of a broad variety of polarization observables that will lead us to a more
complete knowledge of the energy spectrum of nucleons. Further progress on the development of theoretical tools related to the spectrum and structure of excited nucleons is essential to come closer to ameaningful comparison of experiment and theory in this domain of conﬁnement. In presenting selected
results from the past decade. I hope to illustrate progress that has been made both in experiment and in
our understanding of the importance of the N* programs, and well of its vitality. I am conﬁdent the N*
program continues worldwide and especially at the Jeﬀerson Lab accelerator with higher energies andnew instrumentation.
[1] Nathan Isgur, in “Excited Nucleons and Hadronic Structure”, World Scientiﬁc Publishing, 2001, eprint: nucl-th/0007008.

N* Structure: A Window on Strong QCD
Craig Roberts, Argonne National Laboratory
One of the greatest challenges within the Standard Model is to discover the source of visible mass. Indeed,this is the focus of one of the Millennium Problems posed in 2000 by the Clay Mathematics Institute. The
answer is hidden within quantum chromodynamics, the relativistic quantum ﬁeld theory believed to describe nuclear physics; and it is quite likely that revealing the origin of mass will also explain the natureof conﬁnement. In addressing these issues, this presentation will sketch key insights drawn using modern methods to solve the continuum bound-state problem and how they have been informed by modern
experiments on nucleon-to-resonance transition form factors.

09:30
DMSB 123

The MAID Legacy and Future
Lothar Tiator, Johannes Gutenberg University Mainz
MAID was introduced in 1998 as a unitary isobar model for pion photo- and electroproduction on nucleons. It quickly developed into a project that included EtaMAID and KaonMAID for η and K photo-andelectroproduction and in addition a dynamical model DMT, that gives the most reliable predictions forpion photo- and electroproduction in the threshold region up to the ∆(1232).
MAID was constructed in a way to minimize the free parameters, which are mainly for electromagnetic
resonance production of only well established 4-star N and ∆ resonances with hadronic parameters takenfrom PDG. This is probably part of the success, that it did not overﬁt all available data structures, but
used only the substantial degrees of freedom. Up to now it can still provide reliable predictions for newpolarization observables.
MAID has also been used for partial wave analysis, providing single-energy multipoles for photoproduction and single-Q2 transition form factors for up to 10 N and ∆ resonances in the region 0 ≤ Q2 ≤5 GeV2 . The latest update for e, e0 π is MAID2007 and the latest extensions are Two-Pion-MAID in 2007
and ChiralMAID in 2012.
Currently, we are updating EtaMAID, analyzing high precision diﬀerential cross sections from MAMI
and single spin and double beam-target polarization observables from MAMI, ELSA and JLab. Resultswith new and updated ηN and η 0 N branching ratios will be presented. An update for pion photo- andelectroproduction is also planned.

8

10:00
DMSB 123NSTAR 2017 — Book of Abstracts

Sunday, August 20, 2017

Break (Coﬀee / Refreshments)
Time: Sunday, August 20, 2017, 10:30 – 11:00
Room: Sonoco Pavilion

General Session P2
Time: Sunday, August 20, 2017, 11:00 – 12:00
Room: DMSB 123
Chair: Ralf Gothe
Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS
Victor Mokeev, Jeﬀerson Lab
The CLAS detector at Jeﬀerson Lab has provided the dominant part of the available worldwide data on
exclusive meson electroproduction oﬀ protons in the nucleon resonance (N ∗ ) region. A large body of dataon diﬀerential cross sections, as well as single- and double-polarization asymmetries have been obtained
at invariant masses of the ﬁnal state hadrons W < 2.0 GeV and photon virtualities Q2 < 5.0 GeV2 .
The current status and prospects for the extraction of the γv pN ∗ electrocouplings from these data will bepresented. The CLAS data on N π, N η, and pπ + π − electroproduction has provided γv pN ∗ electrocouplings for most N ∗ states in the mass range up to 1.8 GeV. In the near term future, the electrocouplingsof most N ∗ states in the mass range up to 2.0 GeV will be obtained at Q2 < 5.0 GeV2 . In this regard,
the new results on “missing” baryon states recently available from the combined studies of the CLAS
pπ + π − photo- and electroproduction data will be discussed.
Physics analyses of the CLAS results on γv pN ∗ electrocouplings have revealed the N ∗ structure as acomplex interplay between the inner core of three dressed quarks and an external meson-baryon cloud.
The Dyson-Schwinger Equations of QCD have conclusively demonstrated the capability to explore themomentum dependence of the dynamical quark mass (mass function) from the CLAS data on the γv pN ∗electrocouplings of resonances of diﬀerent quantum numbers. The γv pN ∗ electrocoupling studies thatwill be extracted for Q2 < 12 GeV2 in the upcoming experiments with CLAS12 will allow us to explore
the dressed quark mass function in the transition from the conﬁnement to the pQCD regimes of the strong
interaction, which will allow us to address the challenging problems on the nature of > 98% of hadronmass and the mechanisms for quark-gluon conﬁnement.
Studies of high-lying (M > 2.0 GeV) resonance electrocouplings will also shed light on the existenceof new states of baryon matter, the so-called hybrid baryons. The prospects for these studies will be
discussed.

11:00
DMSB 123

Future Facilities and QCD Physics
Bob McKeown

11:30
DMSB 123

Lunch Break
Time: Sunday, August 20, 2017, 12:00 – 13:30

9

NSTAR 2017 — Book of Abstracts

Sunday, August 20, 2017

Parallel Session A1
Time: Sunday, August 20, 2017, 13:30 – 15:00
Room: DMSB 124
Chair: Gernot Eichmann
Duality between resonances and parton physics
Wally Melnitchouk, Jeﬀerson Lab
An overview will be given of recent progress in understanding the duality between the physics of nucleon
resonances and the partonic structure of hadrons.

13:30
DMSB 124

Quark Hadron Duality in Unpolarized Structure Functions
Ioana Niculescu, James Madison University
Quark hadron duality establishes an intriguing connection between medium and high energy physics byidentifying in certain cases dual descriptions of observables either in terms of explicit quark degrees of
freedom or as averages over hadronic variables. Duality has been extensively studied in inclusive electron
scattering experiments Jeﬀerson Lab. The present talk is an overview of these results for unpolarized
structure functions for proton, neutron, and nuclei.

14:00
DMSB 124

Measurements of the Nucleon Spin-Structure Functions in and above the Resonance Region fromthe Hall-B EG1 experiment at Jeﬀerson Laboratory
Robert Fersch, Christopher Newport University
In the EG1 experiment in Hall-B at Jeﬀerson Lab (2000-2001), polarized electrons with energies of
1.6, 2.5, 4.2 and 5.7 GeV were scattered from proton and deuteron targets (NH3 and ND3 dynamically polarized along the beam direction) and detected with CLAS. Virtual photon asymmetries A1
and A2 and nucleon spin structure functions g1 and g2 were measured over a wide kinematic range(0.05 GeV2 < Q2 < 5 GeV2 and 1.08 GeV < W < 3 GeV). These (now available) data are able
to constrain parametrization of world data in the resonance region, oﬀer a better understanding of quarkhadron duality, and provide more precise values of higher-twist matrix elements in the framework of the
Operator Product Expansion.

14:20
DMSB 124

Quark-hadron duality in parity-violating electroweak reactions
Toru Sato, Osaka University

14:40
DMSB 124

Parallel Session B1
Time: Sunday, August 20, 2017, 13:30 – 15:00
Room: DMSB 125
10

NSTAR 2017 — Book of Abstracts

Sunday, August 20, 2017

Chair: David Wilson
Resonance properties via lattice QCD
Raul Briceno, JLab/ODU
Lattice QCD is a powerful, model-independent tool for the determination of hadronic properties directlyfrom QCD. In recent years there has been signiﬁcant progress in our ability to extract increasingly complicated quantities using this approach. In particular, we are ﬁnally at a stage where elastic and inelastic
hadronic amplitudes are being extracted. Also, we have seen the ﬁrst photo-/electro-production calculations. These calculations have been made possible by a series of technological and formal achievements,
some of which I will discuss. The techniques are universal and have been used and tested for a large
variety of channels, resonant as well as non-resonant. I will review some of the more recent numericalresults pertaining to the study of resonant reactions and discuss the information we are able to extract
about resonances on the lattice. I will also give an outlook for where the ﬁeld is heading.

13:30
DMSB 125

Hadron scattering amplitudes from lattice QCD with controlled errors
John Bulava, U. of Southern Denmark and CP3-Origins
Given the impressive improvements in statistical precision that have been achieved in recent lattice QCD
calculations of hadron scattering amplitudes, it is now important to address systematic errors due to the lattice spacing, ﬁnite volume, and reduced symmetry. As a ﬁrst illustration, results for the isovector p-wave
elastic pion-pion scattering amplitude as well as the isovector timelike pion form factor are presented.
Finally, an outlook for meson-baryon scattering amplitudes is discussed.

14:00
DMSB 125

Total decay and transition rates from LQCD
Maxwell Hansen, Helmholtz Institute Mainz
I discuss a new technique for extracting decay and transition rates into ﬁnal states with any number ofhadrons. The approach is only sensitive to total rates, in which all out-states are summed. For processes
involving external currents, diﬀerential rates with respect to the current q 2 may also be extracted. Our
method requires solving the inverse problem of extracting a spectral function from a correlator and also
necessitates a smoothing procedure to give a well-deﬁned inﬁnite-volume limit. Both of these steps areaccomplished by the Backus-Gilbert method and, as we show with a numerical example, reasonableprecision can be expected in cases with multiple open decay channels. Potential applications include
nucleon structure functions and the onset of the deep inelastic scattering regime.

14:20
DMSB 125

Gluon structure of hadrons
Phiala Shanahan, College of William and Mary
I will discuss recent progress in lattice QCD determinations of the gluonic structure of hadrons and nuclei

11

14:40
DMSB 125NSTAR 2017 — Book of Abstracts

Sunday, August 20, 2017

Parallel Session C1
Time: Sunday, August 20, 2017, 13:30 – 15:00
Room: DMSB 126
Chair: Volker Burkert
Conﬁnement in N* and DIS Physics
Latifa Elouadrhiri, Jeﬀerson Lab
A fundamental challenge of modern nuclear physics is to understand the structure of the building blocksof nuclear matter, protons and neutrons, the origin of baryon masses and the conﬁnement of quarks andgluons. Electron scattering is a superb experimental tool to study the internal structure of nucleons at
diﬀering distance scales, as the resolving power of the probe can be varied revealing the nucleon internal
structure, and providing insight into the quark and gluon dynamics and the forces conﬁning them in the
nucleon. The Generalized Parton Distributions (GPDs) provide the theoretical framework to interpretthe experimental data. The CLAS12 detector is scheduled for completion in the fall of 2017. Employing
continuous wave electron beams of up to 12 GeV energy, will enable the user community from aroundthe world to perform precise exclusive experiments in a large kinematical regime to eﬀectively engage
in nuclear imaging and obtaining insight into the forces that conﬁne quarks and gluons in the nucleon. I
will review the landscape of both theory and experiments, and describe the new equipment with focus on
the approved science program for the CLAS12 detector, which will provide the capabilities needed for achallenging experimental program for Nucleon and Nucleon excitation.

13:30
DMSB 126

Unraveling conﬁnement forces with DVCS
Francois-Xavier Girod, JLab
The shear forces and pressure conﬁning partons in the Nucleon are encoded in the space-space components of the Energy-Momentum Tensor (EMT). The matrix elements of the EMT are accessible via
the second Mellin moment of the chiral even Generalized Parton Distributions (GPDs) in Hard Exclusive Scattering. We present a model dependent investigation of parton conﬁnement using Deeply VirtualCompton Scattering (DVCS) on Hydrogen γ ∗ p → γp. We make use of simple approximations to allow
a dispersion analysis of the unpolarized and beam-polarized cross-sections, extracted from existing andprojected data at the CEBAF Large Acceptance Spectrometer in Hall B at Jeﬀerson Lab. The conﬁnement forces are derived from the subtraction constant (D-term) in the dispersion analysis. The validityof those approximations ultimately will be controlled from the knowledge accumulated with the full 12
GeV program at Jeﬀerson Lab.

14:00
DMSB 126

Peripheral transverse densities of the baryon octet from ChPT and dispersion analysis
Astrid Hiller Blin, Universidad de Valencia
Transverse densities describe the distribution of charge and current in hadrons at ﬁxed light-front timeand enable a spatial representation of hadrons as relativistic systems. We report about a recent calculation of the transverse densities of the spin-1/2 ﬂavor-octet baryons at peripheral distances b of the order of 1/Mp i, using methods of relativistic chiral perturbation theory (ChPT) and dispersion analysis
12

14:20
DMSB 126NSTAR 2017 — Book of Abstracts

Monday, August 21, 2017

[arXiv:1703.04534]. The densities are represented as dispersive integrals over the imaginary parts of theform factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion
cut t > 4Mp i2 are calculated using relativistic ChPT including octet and decuplet baryons. The ChPT
calculations are extended into the rho meson mass region using an N/D method that incorporates the pion
electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles.
We compute the peripheral charge and magnetization densities in the octet baryon states, estimate theuncertainties, and determine the quark ﬂavor decomposition. The approach can be extended to baryon
form factors of other operators and the moments of generalized parton distributions.

When are mesons eigenstates of SU(3) versus that of ﬂavor?
Robert Pisarski, Brookhaven National Laboratory
It is well known that the eta’ meson is mainly a SU(3) ﬂavor singlet, while the phi meson is mainly s-bar
s. We give an elementary but general explanation of this using chiral symmetry, introducing the conceptof hetero- and homochiral states, such as the eta’ and phi, respectively. We predict that an excited phi,
and associated states, are heterochiral, so that the excited phi is not mainly s-bar s, but is close to a singlet
in SU(3) ﬂavor. We categorize spin-two mesons, which include both types.

14:40
DMSB 126’Star Wars Musiclipse’ Concert, South Carolina Philharmonic
Time: Sunday, August 20, 2017, 15:30 – 17:30
Room: Koger Center for the Arts

Monday, August 21, 2017

Registration
Time: Monday, August 21, 2017, 07:30 – 09:00
Room: Lobby near DMSB 123

General Session P3
Time: Monday, August 21, 2017, 08:30 – 10:30
Room: DMSB 123
Chair: Lothar Tiator
Spin Asymmetries and Helicity Amplitudes from Pion Production from Polarized Neutrons at
Jeﬀerson Lab
Andrew Sandorﬁ, Jeﬀerson Lab
The spectrum and photocouplings to excited N * states provide benchmark tests for models of nucleon
structure. These require a determination of photoproduction amplitudes and are extracted through detailed
13

08:30
DMSB 123NSTAR 2017 — Book of Abstracts

Monday, August 21, 2017

partial-wave analyses (PWA), which must be ﬁt to many diﬀerent polarization observables to mitigate
ambiguities. Since the electromagnetic interaction is not isospin invariant, the N * photocouplings forneutron and proton targets are diﬀerent. While considerable data has been accumulated in photoproduction reactions with protons, comparatively little information is available from neutron targets, and there
is almost no spin-dependent neutron data. As a result, the photocouplings to states excited from neutrons
are poorly determined. To address such issues, the Jlab E06-101 (g14) experiment was performed during
2011-2012 using the CLAS detector in Hall B with circularly and linearly polarized photons incident on
longitudinally polarized Deuterons in frozen-spin targets of solid Hydrogen-Deuteride (HD). Measurements of the beam-target helicity asymmetry (E) in the γ + n(p) → π − + p(p) reaction, spanning thenucleon resonance region from invariant mass W = 1500 to 2300 MeV, have recently been reported [1].
These will be compared to PWA predictions, along with their extracted photocouplings. Other observables are under study and preliminary results will be presented.
[1] D. Ho et al., Phys. Rev. Lett. 118, 242002 (2017).

Status of the Lambda(1405)
Maxim Mai, George Washington University
Antikaon-nucleon scattering is an important testing ground for our understanding of QCD in the low andintermediate energy regime. Recent high precision data on the energy shift and width of the Kaonichydrogen as well as the lineshape measurements in the pi-Sigma photoproduction experiment at CLAS
have sparked new interest in this interaction channel.
In my talk, I will review the current theoretical progress and how modern experimental data can be used
to reduce the uncertainty of results thereof.

09:00
DMSB 123

From Experimental Data to Pole Parameters in a Model Independent Way (Angular Dependent
Phase Rotations and L+P method)
Alfred Svarc, Rudjer Boskovic Instite
It is well known that unconstrained single-energy partial wave analysis (USEPWA) gives many equivalentdiscontinuous solutions, so a constraint to some theoretical model must be used to ensure the uniqueness.
It can be shown that it is a direct consequence of not specifying the angle-dependent part of continuum ambiguity phase which mixes multipoles, and by choosing this phase we restore the uniqueness of
USEPWA, and obtain the solution in a model independent way [1]. Up to now, there was no reliable way
to extract pole parameters from so obtained SE partial waves, but a new and simple single-channel method(Laurent + Pietarinen expansion) applicable for continuous and discrete data has been recently developed[2-5]. It is based on applying the Laurent decomposition of partial wave amplitude, and expanding the
non-resonant background into a power series of a conformal-mapping, quickly converging power series
obtaining the simplest analytic function with well-deﬁned partial wave analytic properties which ﬁts the
input. The method is particularly useful to analyse partial wave data obtained directly from experimentbecause it works with minimal theoretical bias since it avoids constructing and solving elaborate theoretical models, and ﬁtting the ﬁnal parameters to the input, what is the standard procedure now. The
generalization of this method to multi- channel case is also developed and presented. Tests are performedon Bonn-Gatchina P11 πN partial wave amplitudes taken from BG2011-2 solution [6] by comparing our
results with exact results obtained by analytic continuation [7]. As a demonstration this method is applied to GWU-SAID [8] E1+ and M1+ multipoles. Unifying both methods in succession, one constructs

14

09:30
DMSB 123NSTAR 2017 — Book of Abstracts

Monday, August 21, 2017a model independent procedure to extract pole parameters directly from experimental data without referring to any theoretical model. We give preliminary results for USEPWA of kaon photoproduction on
the world collection of real data. References: [1] A. Svarc, https://indico.cern.ch/event/591374/contributions/2477135/ , PWA9/ATHOS4: The International Workshop on Partial Wave Analyses and Advanced
Tools for Hadron Spectroscopy, Bad Honnef near Bonn (Germany) from March 13 to 17, 2017. [2]A. Svarc, M. Hadzimehmedovic, H. Osmanovic, J. Stahov, L. Tiator, and R. L. Workman, Phys, Rev.
C88, 035206 (2013). [3] A. Svarc, M. Hadzimehmedovic, R. Omerovic, H. Osmanovic, and J. Stahov, Phys, Rev. C89, 0452205 (2014). [4] A. Svarc, M. Hadzimehmedovic, H. Osmanovic, J. Stahov,
L. Tiator, and R. L. Workman, Phys, Rev. C89, 65208 (2014). [5] A. Svarc, M. Hadzimehmedovic,
H. Osmanovic, J. Stahov„ and R. L. Workman, arXiv:1405.6474 [nucl-th], Phys. Rev. C. in press [6]http://pwa.hiskp.uni-bonn.de/BG2014_02_ampl.php [7] E. Gutz, et al, Eur. Phys. J. A (2014)
50: 74 [8] http://gwdac.phys.gwu.edu/analysis/pr_analysis.html

Electromagnetic N* Transition Form Factors in the ANL-Osaka Dynamical Coupled-Channels Approach
Hiroyuki Kamano, KEK
The electromagnetic transition form factors of nucleon resonances (N*) have been being extensively studied because those are expected to be the key to quantitatively disentangling the N* substructures and theirscale dependence in a close relation with experiments.
In this talk, I overview our recent eﬀorts to extract electromagnetic N* transition form factors througha comprehensive analysis of the data for meson electroproduction reactions oﬀ the proton target within
the ANL-Osaka dynamical coupled-channels approach. Here preliminary results for the extracted form
factors associated with low-lying N* resonances will also be presented, with an emphasis on the complexvalued nature of the transition form factors deﬁned by resonance poles.

10:00
DMSB 123

Break (Coﬀee / Refreshments)
Time: Monday, August 21, 2017, 10:30 – 11:00
Room: Sonoco Pavilion

General Session P4
Time: Monday, August 21, 2017, 11:00 – 12:30
Room: DMSB 123
Chair: Jan Ryckebusch
N* Photoexcitation Results from Bonn
Annika Thiel, HISKP, University of Bonn
The dynamics of the quarks and gluons inside the nucleon are a long-standing question in hadron physics.
To shed more light on this topic, the excitation spectrum of the nucleons needs to be measured and compared to theoretical models like constituent quark models or lattice QCD calculations. Until now, several
predicted resonances have not been found by experiments, which is the well-known missing resonances
problem. The excitation spectrum of the nucleon consists of several strongly overlapping resonances,

15

11:00
DMSB 123NSTAR 2017 — Book of Abstracts

Monday, August 21, 2017

which makes it diﬃcult to disentangle and identify them. To determine their exact contributions, a solution of the partial wave analysis has to be found. For a complete experiment, which leads to an unambiguous solution, at least 8 well-chosen single and double polarization observables are needed. With the
CBELSA/TAPS experiment, the measurement of several single and double polarization parameters in
diﬀerent reactions is possible by using a circularly or linearly polarized photon beam on a longitudinallyor transversally polarized butanol target. The CBELSA/TAPS setup provides a nearly 4π angular coverage and a high detection eﬃciency for neutral states, which gives an ideal condition for the study of ﬁnal
states comprising neutral mesons. In this talk results of diﬀerent polarization observables for single anddouble meson photoproduction will be presented. Additionally, the impact of the polarization data will
be shown and an outlook on the further perspectives will be given. Supported by the DFG (SFB/TR16).

Baryon structure and reaction mechanisms from Dyson-Schwinger equations
Gernot Eichmann, IST Lisboa
I will review results for the light baryon spectrum obtained from solving QCD’s three-body Faddeev
equation as well as its quark-diquark simpliﬁcation. Both approaches yield similar results, which underlines the role of diquark correlations within baryons. The resulting baryons carry a rich structure withrelativistically induced orbital angular momentum that would be forbidden in the non-relativistic quark
model. I will further discuss recent progress on the spectrum of strange baryons, nucleon transition form
factors, and a microscopic approach to meson electroproduction.

11:30
DMSB 123

Hybrid Baryon Search at CLAS12
Annalisa D’Angelo, University and INFN Rome Tor Vergata
A program has been approved at JLAB to search for new excited baryon states in the mass range from 1.8
GeV to 3 GeV with CLAS12. For the ﬁrst time the behavior of resonance electrocouplings over the full
spectrum of excited proton states will be studied at very low photon virtualities, approaching the photon
point. The experiment will measure ΚΛ, ΚΣ0 and π+π- p exclusive ﬁnal states using longitudinallypolarized electron beams of 6.6 GeV and 8.8 GeV, to cover the range of invariant masses up to 3 GeV. By
studying the Q2 evolution of electroexcitation amplitudes it will be possible to distinguish between regular
N* states and possible additional hybrid baryon states, with the glue as an extra constituent component
beyond the three constituent quarks.

Lunch Break
Time: Monday, August 21, 2017, 12:30 – 13:30

Total Solar Eclipse - Reception
Group Photo
Total Solar Eclipse - Main Event, 2 min 30 sec in Columbia - 14:43
Time: Monday, August 21, 2017, 13:30 – 16:30
Room: DMSB Rooftop

16

12:00
DMSB 123NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

“Laying the God Particle to Rest”; Public Lecture by Craig Roberts
Time: Monday, August 21, 2017, 17:30 – 19:00
Room: DMSB 101

Tuesday, August 22, 2017

General Session P5
Time: Tuesday, August 22, 2017, 08:30 – 10:30
Room: DMSB 123
Chair: Annalisa D’Angelo
Developments of the Julich-Bonn Dynamical Coupled-Channel Analysis
Michael Doering, George Washington University
Results for baryon spectroscopy by the Julich-Bonn collaboration and other groups will be reviewed.
Highlights contain common eﬀorts of diﬀerent phenomenology groups and the impact of recent highprecision data from ELSA, JLab, MAMI, and other facilities. Questions will be addressed of how toproceed to reach conclusive answers in baryon spectroscopy and how phenomenology can be connectedto theory in a meaningful way. Formal S-matrix constraints and statistical aspects for the determinationof the scattering amplitude and resonance content will be discussed.

08:30
DMSB 123

Understanding the Spectrum of Excited Nucleons using CLAS at Jeﬀerson Lab
Volker Crede, Florida State University
Baryons are complex systems of conﬁned quarks and gluons and exhibit the characteristic spectra of
excited states. These states are sensitive to the details of quark conﬁnement, which is only poorly understood with quantum chromodynamics (QCD), the fundamental theory of the strong interaction. To gain
insight into this complex dynamics, the nucleon excitation spectrum has been studied for many years. The
key question remains what are the relevant degrees of freedom for the resonance physics of QCD. Are
the so-called constituent quarks the most eﬃcient way to describe reaction amplitudes and the excitation
spectrum of QCD with light quarks? To what extent are diquark correlations, gluonic modes or hadronic
degrees of freedom important in this physics? On the experimental side, high-energy electrons and photons are a remarkably clean probe of hadronic matter. Signiﬁcant progress has been achieved with therecent high-statistics polarization data from Jeﬀerson Lab using the CEBAF Large Acceptance Spectrometer (CLAS) and combining polarized tagged-photon beams with polarized targets. Such experiments areimportant steps toward so-called complete experiments that will allow us to unambiguously determine
the scattering amplitudes in the underlying reactions and to identify nucleon resonance contributions in
amplitude analyses. In this presentation, I will discuss recent results from the experimental N* programat Jeﬀerson Lab.

17

09:00
DMSB 123NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

N* Photoexcitation Results from Mainz
Vahe Sokhoyan, University of Mainz, Institute for Nuclear Physics
The A2 Collaboration performs a manifold research program using real photons in the Crystal Ball/TAPS
experiment at the MAMI accelerator facility in Mainz. The experiments are carried out with highintensity unpolarized, linearly or circularly polarized photon beams, and unpolarized or polarized targets.
The Crystal Ball/TAPS setup provides almost complete coverage in solid angle and is well suited for thedetection of multi-particle ﬁnal states. In order to probe the internal structure of the nucleon, the spectrumof baryon resonances is studied via measurements of unpolarized cross-sections and various polarization
observables in single and double meson photoproduction. Furthermore, experiments with light and heavy
nuclear targets are carried out to study the production of mesons oﬀ neutrons and to investigate modiﬁcations of baryons in the nuclear medium. In this talk, recent results, the current status, and future plansfor new experiments at MAMI will be presented.

09:30
DMSB 123

Supersymmetric features of hadron physics and other novel properties of QCD from Light-Front
Holography and Superconformal Quantum Mechanics
Stanley J. Brodsky, SLAC National Accelerator Laboratory, Stanford University
A primary question in hadron physics is how the mass scale for hadrons emerges from the QCD Lagrangian, even in the limit of zero quark mass. I will present a new approach to color conﬁnement andthe emergence of the QCD mass scale, based on ‘’light-front holography”, a formalism which relates
the bound-state amplitudes in the ﬁfth dimension of AdS space to the boost-invariant light-front wavefunctions describing the structure of hadrons in physical space-time. The result is a nonperturbative,
relativistic light-front quantum mechanical wave equation which incorporates color conﬁnement and predicts the spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark
mass, form factors, structure functions, as well as linear Regge trajectories with identical slopes in theradial quantum number n and orbital angular momentum L for both mesons and baryons. One can extend
the analysis using superconformal algebra where the hadronic eigensolutions form 2 X 2 supersymmetricrepresentations of the conformal group. The resulting light-front bound-state equations predict striking
similarities between the meson, baryon, and tetraquark spectra. The mass scale underlying the masses ofthe light-quark hadrons also determines the mass scale Λs which controls the evolution of the perturbative QCD coupling. The predicted hadronic light-front wavefunctions lead to a new understanding of theconversion of quarks and gluons to hadrons and jet hadronization at the amplitude level.
I will also discuss (1) a new mechanism for Higgs production at high longitudinal momentum at the
LHC, and (2) applications of the Principle of Maximum Conformality (PMC), which sets the renormalization scale of perturbative QCD predictions for LHC reactions at every order unambiguously. The PMC
predictions are independent of the choice of renormalization scheme and eliminate the n! renormalon divergence.

Break (Coﬀee / Refreshments)
Time: Tuesday, August 22, 2017, 10:30 – 11:00
Room: Sonoco Pavilion

General Session P6
Time: Tuesday, August 22, 2017, 11:00 – 12:30
18

10:00
DMSB 123NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Room: DMSB 123
Chair: Alfred Svarc
Chiral Unitary and New Developments in the Baryon Sector
Eulogio Oset, Universidad de Valencia
I shall report on recent developments combining chiral dynamics of meson baryon interaction and thegeneration of some resonances, together with mechanisms that develop a triangle singularity and are responsible for further stabilizing the resonances, the explanation of some particular decay modes, or the
explanation of some experimental peaks. Examples of them are the explanation of the πN ∗ (1535) contribution in the γp → pπ 0 η reaction, the peak observed in the γp → K + Λ(1405) reaction around 2110
MeV, the πN ∗ (1535) and f0 (500)N decay modes of the N ∗ (1875) and the π∆ decay of the N ∗ (1700).

11:00
DMSB 123

N* Production from e+ e− Annihilation
Bing-Song Zou, Institute of Theoretical Physics, CAS
Up to now, the N* production from e e annihilations has been studied only around charmonium region.
Charmonium decays to N*’s are analogous to (time-like) EM form factors in that the charm quark annihilation provides a nearly pointlike (ggg) current. Complementary to other sources, such as eN , KN
and π − N reactions, this new source for N* spectroscopy has a few advantages, such as an isospin ﬁlter
and a low spin ﬁlter. The experimental results on N* from e+ e− annihilations and their phenomenological implications are reviewed. Possible new sources on N* production from e+ e− annihilations are
discussed.
+ −

11:30
DMSB 123

Valence-quark structure in nucleon resonances from DSEs
Jorge Segovia, Technische Universität München
Nonperturbative quantum chromodynamics poses signiﬁcant challenges. Primary amongst them is a needto chart the behaviour of QCD’s running coupling and masses into the domain of infrared momenta.
Contemporary theory is incapable of solving this problem alone but a collaboration with experimentholds a promise for progress. This eﬀort can beneﬁt substantially by exposing the structure of nucleon
excited states and measuring the associated transition form factors at large momentum transfers. Largemomenta are needed in order to pierce the meson-cloud that, often to a signiﬁcant extent, screens the
dressed-quark core of all baryons; and it is via the Q2 -evolution of form factors that one gains access to
the running of QCD’s coupling and masses from the infrared into the ultraviolet.
We present a uniﬁed QCD-based description of elastic and transition form factors involving the nucleon
and its resonances. We compare predictions made using a framework built upon a Faddeev equation
kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a conﬁning, symmetry-preserving treatment of a vector ⊗ vector contact-interaction in a widely-usedleading-order (rainbow-ladder) truncation of QCD’s Dyson-Schwinger equations. This comparison explains that the contact-interaction framework produces hard form factors, curtails some quark orbital
angular momentum correlations within a baryon, and suppresses two-loop diagrams in the elastic andtransition electromagnetic currents. Such defects are rectiﬁed in our QCD-based approach and, by contrasting the results obtained for the same observables in both theoretical schemes, shows those objects
which are most sensitive to the momentum dependence of elementary quantities in QCD.
19

12:00
DMSB 123NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Lunch Break
Time: Tuesday, August 22, 2017, 12:30 – 14:00

IAC Meeting
Time: Tuesday, August 22, 2017, 12:30 – 14:00
Room: Sonoco Pavilion

Parallel Session A2
Time: Tuesday, August 22, 2017, 14:00 – 15:30
Room: DMSB 124
Chair: Volker Credeγn → pπ − Cross Section Measurement at CLAS
Paul Mattione, Jeﬀerson Science Associates
Measuring the spectrum of N ∗ resonances will provide valuable information on the degrees of freedom
within the nucleon, shedding light on whether there are signiﬁcant contributions from correlated quarkpairs, or diquarks. To extract these states, measurements of both γp and γn cross sections are necessary
to disentangle the isospin components of the photoproduction amplitudes.
A measurement of the γn → pπ − diﬀerential cross section will be shown using data from the Jeﬀerson Lab CLAS g13 experiment. These results were determined by ﬁrst measuring the cross section for
γd → pπ − (p), and then by performing a correction for ﬁnal-state interactions in the target deuteron.
From these data, the ﬁrst-ever determination of the excited neutron multipoles for the N (1440)1/2+ ,N (1535)1/2− , N (1650)1/2− , N (1720)3/2+ resonances will be shown. These cross section data are
a factor of 2.5x more than the world data set for this channel, providing important constraints needed toadvance coupled-channel analysis ﬁts that are sorely lacking γn data.

14:00
DMSB 124

Polarization Observables in Meson Photoproduction with the Crystal Ball/TAPS at MAMI
Natalie Walford, University of Basel
A comparison of experimentally observed excited nucleon states to model predictions or lattice QCD
calculations is made, large diﬀerences arise, speciﬁcally concerning the number of excited states. In
order to fully understand the strong interaction in the non-perturbative region, the excitation spectrum of
nucleons is an important tool to use. The electromagnetic coupling of photons to protons is diﬀerent thanthat of neutrons in certain states. Several experimental facilities have dedicated programs to measurepolarization observables in diﬀerent photoproduction reactions including the Crystal Ball/TAPS setup
at the MAMI accelerator in Mainz, Germany. A complete partial wave analysis (PWA) can assist inyielding more information about any reaction with polarization observables playing a crucial role. Spinobservables are essential in disentangling the contributing resonant and non-resonant amplitudes, whereas
cross-section data alone is not suﬃcient for separating resonances. Preliminary results of polarization
observables (E, T , and F ) of η, single, and double π production will be shown with comparison topredictions of recent multipole analyses. These results will allow for signiﬁcantly increasing the world
database on these reactions.
20

14:30
DMSB 124NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Determination of the Hyperon Induced Polarization and Polarization–Transfer Coeﬃcients for
Quasi-Free Hyperon Photoproduction oﬀ the Bound Neutron
Colin Gleason, University of South Carolina
Many excited states (N ) predicted by quark models, but not observed in πN channels, are expected tocouple strongly to kaon–hyperon (KY) channels. While in the last decade data has been published for
KY photoproduction oﬀ the proton, data oﬀ the neutron are scarce. In this talk we will show preliminaryCMresults for P , Cx , and Cz for the reaction γd → K 0 Λ(p) for Eγ between 0.9–2.6 GeV and cosθK0
between -0.9–1. The data was collected in experiment E06-103 (g13) with the CLAS detector at Thomas
Jeﬀerson National Accelerator Facility using a circularly polarized photon beam and an unpolarized LD2target. We will discuss the eﬀect of neutron binding on the observables and the comparison of our resultswith theoretical predictions. Our study is part of a larger eﬀort by the g13 group to provide cross–sections
and polarization observables for meson photoproduction oﬀ the neutron and is expected to have a large
impact on the N ∗ research.
∗

14:50
DMSB 124

Beam-Target Asymmetry for γn(p) → π − p(p) in N ∗ Resonance Region
Haiyun Lu, University of Iowa
The excited-state spectrum of the nucleon is a complicated overlap of many resonances that must be disentangled through multipole analyses of reaction amplitudes. Meson photoproduction, which has beena fruitful probe of N∗ structure, requires data on many diﬀerent polarization observables to constrain its
four complex amplitudes. While considerable data has been accumulated with proton targets, comparatively little information is available from neutron targets. Recently, the ﬁrst beam-target helicity asymmetries with circular beam polarization in the γn(p) → π − p(p) reaction have been reported in PhysicalReview letters 118, 242002 (2017). This talk presents a parallel analysis from the same experiment of
the beam-target double-polarization observable “G” with linearly polarized beam for the same reaction.
Linearly polarized photons and longitudinally polarized deuterons in a solid hydrogen deuteride (HD)target were used with the CEBAF Large Acceptance Spectrometer (CLAS) at Jeﬀerson Lab (JLab). Data
are combined to extract the beam (Σ) and beam-target (G) asymmetries. Preliminary results for the Σobservables are consistent with measurements from the g11 experiment at JLab and theoretical model
predictions. The energy and angular dependence of G will be reported, together with comparisons topredictions from existing partial wave analyses.

15:10
DMSB 124

Parallel Session B2
Time: Tuesday, August 22, 2017, 14:00 – 15:10
Room: DMSB 125
Chair: Raul Briceno
An a0 resonance from lattice QCDDavid Wilson, Trinity College Dublin
I will discuss a recent coupled-channel scattering calculation in a0 quantum numbers by the Hadron Spectrum Collaboration. Utilising the variational method with large bases of operators, including those that
resemble q-qbar and meson-meson like constructions, many energy levels can be extracted. These spectra
are then used with the coupled-channel extensions of Lüscher’s ﬁnite volume formalism, to determine
21

14:00
DMSB 125NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

the inﬁnite volume coupled-channel scattering amplitudes. The resonance poles of these amplitudes arethen studied.

Beyond nucleon properties from lattice QCD
Zohreh Davoudi, University of Maryland - College Park
Over the past decade , ﬁrst-principles lattice QCD calculations of the spectral and structure properties inthe single-nucleon sector have been extended to the multi-nucleon sector, with rapid progress in computational technologies and theoretical understanding. This talk reviews some of the recent progress in thisfront. Among the results that will be brieﬂy presented are the hadronic interactions, and nuclear matrix
elements for nuclear reactions and nuclear structure. The challenges in moving towards lattice QCD calculations of light nuclear systems at lighter quark masses will be discussed, along with the impact of the
precision results in this area on the theoretical and experimental program in nuclear and particle physics.

14:30
DMSB 125

A lattice QCD study of pion-nucleon scattering in the Roper channel
Luka Leskovec, University of Arizona
We present a lattice QCD study of the puzzling positive-parity nucleon channel, where the Roper resonance N ∗ (1440) resides in experiment. The study is based on an ensemble of gauge conﬁgurations
with Nf = 2 + 1 Wilson-clover fermions with a corresponding pion mass of 156 MeV and lattice size
L = 2.9fm. We use several qqq interpolating ﬁelds combined with N π and N σ two-hadron operators
in calculating the energy spectrum in the rest frame. Combining experimental data with the Luescher
formalism implies an additional energy level in the spectrum near the Roper mass mR = 1.43GeV for
our lattice. We do not observe any such additional energy level, which implies that N π elastic scattering
alone does not render a low-lying Roper resonance. The current status indicates that the N ∗ (1440) mightarise as dynamically generated resonance from coupling to other channels, most notably the N ππ.

14:50
DMSB 125

Parallel Session C2
Time: Tuesday, August 22, 2017, 14:00 – 15:30
Room: DMSB 126
Chair: Douglas Hasell
Experimental Advances in Two-Photon Contributions to Lepton-Proton Scattering
Michael Kohl, Hampton University
The famous discrepancy between measurements of the proton electric-to-magnetic form factor ratio withpolarized and unpolarized methods has generated signiﬁcant interest both experimentally and theoretically. The widely preferred explanation of the discrepancy has been hard two-photon exchange, which
had been a neglected piece of the radiative corrections. A variety of experiments have been conceived
and carried out to probe the eﬀects of hard two-photon exchange on various observables, and to quantify
the eﬀect itself which can only be calculated with prior knowledge of hadronic structure. I will introduce
the subject of two-photon exchange with an overview of the experimental status.
This work has been supported by NSF and DOE.
22

14:00
DMSB 126NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Two-photon exchange contribution to elastic electron-proton scattering
Mikhail Yurov, University of Virginia
Two experimental techniques, Rosenbluth separation and recoil polarization transfer, used to extract proGE
ton’s electromagnetic form factors ratio G
yield markedly diﬀerent results. Modern theoretical calcuM
lations suggest that two-photon exchange (TPE) might be responsible for the observed discrepancy andthat it is ε dependent.
Jeﬀerson Lab Experiment E05-017 was designed to measure the TPE contribution over a wide range of εand Q2 . In contrast with the conventional Rosenbluth method, E05-017 detected the elastically scatteredproton rather than the electron. This approach returns a much more precise extraction of the form factor
ratios. While comparisons of e+ p and e− p scattering have been used to constrain TPE at low Q2 , ourmeasurements provide additional information on the ε dependence at low Q2 , and can constrain the sizeof TPE at much larger Q2 values.
After a brief description of the experimental goals and techniques, the current status of the analysis will
be presented. Preliminary results will be shown.

14:30
DMSB 126

Lepton mass eﬀects in two-photon exchange theory
Oleksandr Koshchii, The George Washington University
The future MUSE [1] experiment, which is devised to solve the “Proton Radius Puzzle”, is going to directly measure two-photon exchange (TPE) eﬀects by studying the asymmetries in elastic e± and µ±
scattering. Kinematic conditions of this experiment do not permit us to employ a widely used ultrarelativistic (ml → 0) approximation in calculation of muonic TPE in MUSE. This means that the standard
soft-photon (model-independent) TPE estimations have to be revised to include the mass of the lepton in
ﬁnal expressions. In addition, helicity-ﬂip transitions, which are proportional to the mass of the lepton
and that are usually neglected in scattering of ultrarelativistic electrons, needs to be taken into account,
as well. These transitions describe dynamic properties of the proton and they will make a diﬀerence incomparison of electron vs muon scattering in MUSE. In our talk, we will present our model-independent
charge asymmetry predictions for scattering of unpolarized and massive leptons on proton targets, estimated based on the soft-photon approximation calculation [2]. In addition, we will discuss our recent
results on calculation of the major helicity-ﬂip contribution that is represented by a scalar σ meson exchange in the t-channel [3].
[1] R. Gilman, E. J. Downie, G. Ron, et al. (MUSE), arXiv:1303.2160 [2] O. Koshchii, A. Afanasev,
arXiv:1705.00338 [3] O. Koshchii, A. Afanasev, Phys. Rev. D 94, 116007 (2016)

14:50
DMSB 126

Two-photon exchange correction in elastic lepton-proton scattering. Dispersive and model calculations
Oleksandr Tomalak, JGU Mainz
In view of the proton form-factor problem and proton radius puzzle, the two-photon exchange (TPE)
corrections require a model-independent investigation as the largest source of the hadronic uncertainty
in modern experiments. I present the dispersion relation approach based on unitarity and analyticity
to evaluate the TPE in the elastic electron-proton scattering. The leading elastic and ﬁrst inelastic πNintermediate state contributions are accounted for in the region of small momentum transfer Q2 . 1 GeV2
based entirely on data input. The novel methods of the analytical continuation allowed to exploit the
MAMI form factor data and the MAID parameterization for the pion electroproduction amplitudes as an
23

15:10
DMSB 126NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

input in the calculation. The results are compared to the recent CLAS, VEPP-3 and OLYMPUS data
as well as the full TPE correction in the near-forward approximation, which is based on the Christy
and Bosted unpolarized structure functions ﬁt. Additionally, predictions are given for a forthcoming
muon-proton scattering experiment (MUSE) within the hadronic model.

Parallel Session D2
Time: Tuesday, August 22, 2017, 14:00 – 15:30
Room: DMSB 122
Chair: Toru Sato
Analyticity Constraints for the Baryon Spectrum
Vincent Mathieu, Jeﬀerson Lab
There are several experiments in Europe (COMPASS, LHCb), USA (CLAS, GlueX) and Asia (BES,
Belle) devoted to hadron spectroscopy. In this talk, their goals and prospects are presented with a special
emphasis on the discovery of new ‘exotic’ resonances. There are indeed indications from these experiments about resonances (hybrid mesons, glueballs, tetraquarks, etc) beyond the quark model classiﬁcation. However a close collaboration between theorists and experimentalists is necessary to draw robust
conclusions about their existence.
To this end the Joint Physics Analysis Center (JPAC) was set up between Jeﬀerson Lab and Indiana
University. Its goal is to provide the theoretical framework, based on the principles of the S-Matrix
theory, for the analysis of hadron spectroscopy experiments data. Our main results concern baryons (theN*, Delta, Lambda and Sigma baryon resonances), light mesons (eta, omega and phi) decays and heavy
meson (“XYZ states”) spectroscopy. With the advent of the GlueX detector at the Jeﬀerson Lab, we also
working on the photoproduction of mesons (pion, eta, rho and omega). In this talk, I will present themain results of the JPAC concerning some of the various projects mentioned above.
In particular, I will focus on the analyticity constraints on amplitude construction, their implementation
on baryon analysis.
To facilitate the interactions with the community a interactive webpage, where the models
can be dowloaded and simulated, was recently created: http://www.indiana.edu/ jpac/index.html<http://www.indiana.edu/ jpac/index.html> In the talk, I will also present and show the main featuresof this website.

14:00
DMSB 122

Finite-Energy Sum Rules in Eta Photoproduction oﬀ the Nucleon
Jannes Nys, Ghent University
Pseudoscalar-meson photoproduction on the nucleon is of current interest for hadron reaction studies. At
low energies it provides information about the nucleon spectrum, while at high energies it reveals detailsof the residual hadron interactions due to cross-channel particle (Reggeon) exchanges. These two regimes
are analytically connected, a feature that can be used to relate properties of resonances in the direct channel
to Reggeons in the cross channels. In practice this can be accomplished through dispersion relations andﬁnite-energy sum rules (FESR) [1].
At high energies (Elab>4 GeV), only the unpolarized diﬀerential cross section has been measured, providing little constraints on theoretical models. Forthcoming data from the GlueX experiment at Jeﬀerson
Lab are expected to improve the situation.
24

14:30
DMSB 122NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Even though photons couple to both isospin I=0,1 states, there are some notable diﬀerences between
high energy photoproduction of the η (I=0) and the π0 (I=1). In contrast to the η, the π0 diﬀerential crosssection has a dip in the momentum transfer range, −t∼0.5−0.6 GeV2. The dip in π0 photoproduction
is expected to be associated with zeros in the residues of the dominant ρ/ω Regge exchanges [2,3]. It
is an open question, what mechanisms are responsible for ﬁlling in the dip in eta photoproduction. It is
often assumed that large unnatural contributions come into play. Finite-energy sum rules can provide
clues here by relating the t-dependence of Regge amplitudes to that of the low-energy amplitude, usuallydescribed in terms of a ﬁnite number of partial waves. Early attempts could not resolve this issue due to thelow quality of the data and the large uncertainties in the parametrization of the partial waves. Nowadays,
however, there are several models that have been developed for the resonance region of η photoproduction
allowing for a more precise FESR analysis.
The largest uncertainty in η photoproduction stems from the unnatural parity Regge exchanges. These
contributions can be isolated through photon beam asymmetry measurement. Such measurement willsoon be published by the GlueX collaboration. The experiment uses linearly polarized photons withenergy Elabγ∼9 GeV and it has simultaneously measured η and π0 production. Those data will reduce
the systematic uncertainties and provide a better constraint on Regge amplitudes.
We have analyzed γN→ηN within a FESR framework [4]. Using these sum rules, one is able to obtainthe t-dependence of the high-energy Regge residues using low-energy models. We found that a residue
nonsense-wrong signature zero (NWSZ) seems to be lacking in the t-channel helicity ﬂip amplitude of theρ residue. Including this in our model results in a mechanism where the dip in η photoproduction is ﬁlled
up with natural contributions, rather than genuinely assumed unnatural b exchange [5]. The upcoming
GlueX results will be able to either conﬁrm or refute this explanation: photon beam asymmetry closeto Σ=+1 within the range −t≈0.5−0.6 GeV2 indicate that the absence of a dip in eta photoproduction
should indeed be attributed to natural exchanges.
[1] V. Mathieu, I. V. Danilkin, C. Fernández-Ramı́rez, M. R. Pennington, D. Schott, A. P. Szczepaniak,
and G. Fox, Phys. Rev. D92, 074004 (2015). [2] V. Mathieu, G. Fox, and A. P. Szczepaniak, Phys. Rev.
D92, 074013 (2015). [3] V. Mathieu et al., In preparation. [4] J. Nys, V. Mathieu, C. Fernández-Ramı́rez,
A. N. Hiller Blin, A. Jackura, M. Mikhasenko, A. Pilloni, A. P. Szczepaniak, G. Fox, and J. Ryckebusch(JPAC), (2016), arXiv:1611.04658 [hep-ph]. [5] F. D. Gault and A. D. Martin, Nucl. Phys. B32, 429(1971).

Studying the Pc(4450) resonance in J/psi photoproduction oﬀ protons
Astrid Hiller Blin, University of Mainz
The LHCb has reported the observation of a resonancelike structure, the Pc(4450), in the J/psi p spectrum.
In our work, we discuss the feasibility of detecting this structure in J/psi photoproduction, e.g. in themeasurement that has recently been approved for the CLAS12 experiment at JLab.
We take into account the experimental resolution eﬀects, and perform a global ﬁt to world J/psi photoproduction data, predicting that it will be possible to observe a sizable cross section close to the J/psi
production threshold. We present a ﬁrst estimate of the upper limit for the branching ratio of the Pc(4450)
into the J/psi p channel, and we study the angular distributions of the diﬀerential cross sections. This willshed light on the nature and couplings of the Pc(4450) structure in the future photoproduction experiments.

25

14:50
DMSB 122NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Constituent Counting Rules and Exotic Hadrons
Richard Lebed, Arizona State University
The constituent counting rules, i.e., the scaling behavior of amplitudes (in terms of the number of fundamental constituents) for exclusive processes when high energy scales are present, have been known
for decades, and have been borne out in a number of experiments. Such scaling would be sensitive, inparticular, to possible exotic multiquark content. Here we examine how one may use the rules to testfor pentaquarks in electroproduction, or for tetraquarks in e+ e− annihilation. An interesting new typeof scaling (separate Mandelstam s and t behavior) arises in the forward scattering direction. The correct
scaling arises naturally in AdS/QCD, in which the amplitudes can be computed explicitly.

15:10
DMSB 122

Break (Coﬀee / Refreshments)
Time: Tuesday, August 22, 2017, 15:30 – 16:00
Room: Sonoco Pavilion

Parallel Session A3
Time: Tuesday, August 22, 2017, 16:00 – 18:10
Room: DMSB 124
Chair: Andrew Sandorﬁ
Advances in N* spectroscopy from Exclusive Photoproduction at CLAS
Eugene Pasyuk, Jeﬀerson Lab
This year marks 70th anniversary of the discovery of pion. Just two years later the ﬁrst pion photoproduction experiment was carried out. Another three years passed and the ﬁrst nucleon resonance was observedin pion nucleon scattering. That was the beginning of the nucleon resonance era. The latest edition of
the Review of the Particle Physics lists 60 non-strange baryons. But there are still more states predicted
than observed. Until late 90’s of the 20th century most of the data on the nucleon resonances came frompion nucleon scattering. Over the last two decades the focus was shifted to the photoproduction experiments. CEBAF Large Acceptance Spectrometer, CLAS, is one of the major contributors to this ﬁeld. An
overview of the results of the photoproduction experiments with CLAS will be presented.

16:00
DMSB 124

Photoproduction of ω Mesons using CLAS at Jeﬀerson Laboratory
Zulkaida Akbar, The Florida State University
The spectrum and properties of the excited states of baryons reveal the dynamics and degrees of freedom of the interaction within them. Higher-lying excited states are generally predicted to have strong
couplings to a heavier meson, e.g. to one of the vector mesons, ρ, ω, φ. Therefore, vector-meson studies are important to search for the so-called missing baryon resonances. Photoproduction of ω mesons
was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jeﬀerson Lab. Two observables have been measured from the reaction γp → pω: The diﬀerential cross section and the doublepolarization observable E. The observables were measured using the decay mode ω → π + π − π 0 . The
diﬀerential cross section measurement was performed using circularly-polarized photons produced from

26

16:30
DMSB 124NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

bremsstrahlung of longitudinally-polarized electrons with the tagged photon energies up to 5.7 GeV, incident on an unpolarized liquid hydrogen target. The double-polarization observable E was measured using
circularly-polarized photons for an energy range up to 2.4 GeV and the longitudinally-polarized FrozenSpin Butanol Target (FROST). The diﬀerential cross section as well as the polarization observable allow
us to ﬁnd N∗ resonances decaying to pω through multi-channel Partial Wave Analysis (PWA) that has
been developed for the ω channel. The observables also provide a probe to test theoretical models on the
production mechanism of ω mesons and also the scaling behavior of the cross section. We found that theγp → pω diﬀerential cross section at higher energies exhibits a scaling behavior as predicted by pQCD.

Polarization Observables in γp → K + + Λ and K + + Σ0 Using Circularly Polarized Photons on a
Polarized Frozen Spin Target
Natalie Walford, The Catholic University of America
The search for undiscovered excited states of the nucleon continues to be a focus of experiments at theThomas Jeﬀerson National Accelerator Facility (JLab). A large eﬀort was done using the CEBAF Large
Acceptance Spectrometer (CLAS) detector to provide the database, which will allow nearly modelindependent partial wave analyses (PWA) to be carried out in the search for such states. Polarization
observables play a crucial role in the eﬀort, as they are essential in disentangling the contributing resonant and non-resonant amplitudes. Recent coupled-channel analyses have found strong sensitivity of the
K + + Λ channel to several higher mass nucleon resonances. In 2008 and 2010, double-polarization data
were taken at JLab using circularly and linearly polarized tagged photons incident on a longitudinallyand transversely polarized frozen spin butanol target (FROST), operated at the temperature of 30 mK.
The reaction products were detected in CLAS. This work is based on the analysis of FROST data and theextraction of the E, Lx , Lz , T , F , Tx , and Tz asymmetries of the K + Λ and K + Σ0 ﬁnal states and theircomparison to predictions of recent multipole analyses. There are very few published measurements of
the T asymmetry and none for the E, Lx , Lz , F , Tx , and Tz asymmetries for the K + Λ ﬁnal state. The
K + Σ0 ﬁnal state has no published measurements for these asymmetries. This work is the ﬁrst of its kind
and will signiﬁcantly broaden the world database for these reactions.

16:50
DMSB 124

Measurement of polarization observables for Lambda in the reaction γp → K + Λ
Shankar Adhikari, Florida International University
Spin observables are important to understand the production mechanisms of hyperons, as well as thecontribution of intermediate baryon resonances. Lambda polarizations have been studied extensively inthe recent decades using the reaction γp → K + Λ. This talk presents the measurement of transferred polarization coeﬃcients Cx and Cz , and the induced polarization P, using a new set of high statistics data,obtained using the CEBAF Large Acceptance Spectrometer (CLAS) detector at the Jeﬀerson lab. The
photon beam energy range is 1.117 to 5.45 GeV. These results (Cx , Cz and P ) are extracted simultaneously using Maximum Likelihood Method. The measurements for Cx and Cz represents nearly one orderof magnitude increase in statistics. These results also extended the kinematic range for W > 2.46 GeV,
important for understanding the non-resonant contributions.

27

17:10
DMSB 124NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Polarization observables in double charged pion photo-production with circularly polarized photons oﬀ transversely polarized protons
Lelia Net, University of South Carolina
The study of excited states of the nucleon facilitates the understanding of the nucleon structure and its
underlying symmetry and couplings. A main goal of the N ∗ program at the Thomas Jeﬀerson National
Accelerator Facility is to investigate the excitation and decays of the baryon resonances and assist in identifying the “missing” nucleon resonances that are predicted by theoretical models. One way to study the
nucleon resonances is by extracting polarization observables, which provide more information than theunpolarized cross-section studies, e.g. access to the transition amplitudes of the reaction. Double-pion
photoproduction is the dominating process at high energies, having the largest cross-section, and thus
it plays an important role in probing the nucleon resonance spectrum. The CLAS g9b (FROST) experiment at Thomas Jeﬀerson National Accelerator Facility provided double-pion photoproduction data usingtransversely polarized protons and circularly polarized photons, with energies up to 3.0 GeV. Beam- andtarget-polarization asymmetries were measured and the polarization observables I , Px , Py , Px , Py
were extracted for the γp → pπ + π − reaction. The results are reported and compared with the calculations of an eﬀective Lagrangian model. The data will help deepen the current knowledge of hadronicresonance decays and possibly assist in identifying new baryon resonances via PWA (Partial Wave Analysis) and in this way will contribute to a more comprehensive understanding of the strong interaction.

17:30
DMSB 124

Polarization Observables T and F in the p(γ, π 0 )p Reaction
Hao Jiang, University of South Carolina
The theory that describes the interaction of quarks is Quantum Chromodynamics (QCD), but how quarks
are bound inside a nucleon is not yet well understood. Pion photoproduction experiments reveal important
information about the nucleon excited states and the dynamics of the quarks within it and thus provide a
useful tool to study QCD. Detailed information about this reaction can be obtained in experiments thatutilize polarized photon beams and polarized targets.
Pion photoproduction in the γp → π 0 p reaction has been measured in the FROST experiment at theThomas Jeﬀerson National Accelerator Facility. In this experiment circularly polarized photons withelectron-beam energies up to 3.082 GeV impinged on a transversely polarized frozen-spin target. Finalstate protons were detected in the CEBAF Large Acceptance Spectrometer. Results of the polarization
observables T and F have been extracted. The data generally agree with predictions of present partial
wave analyses, but also show marked diﬀerences. The data will constrain further partial wave analyses and improve the extraction of proton resonance properties. This work is supported in parts by NSF
PHY-1505615.

17:50
DMSB 124

Parallel Session B3
Time: Tuesday, August 22, 2017, 16:00 – 17:50
Room: DMSB 125
Chair: Bingsong Zou
Photo- and Electroexcitation of Bound Neutrons and Protons
Satoshi Nakamura, Universidade Cruzeiro do Sul

16:00
DMSB 12528

NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Data for photon- and electron-induced meson productions oﬀ the deuteron are primary source to assesstransition form factors that excite the neutron to resonances. However, extracting the transition form factors from the data is not trivial due to nuclear eﬀects such as the Fermi motion and ﬁnal state interactions(FSI). In this talk, we develop a model for pion photoproductions on the deuteron taking account of these
nuclear eﬀects. We study how much the FSI change unpolarized and polarized cross sections for the pion
photoproductions oﬀ the deuteron. Then we also examine if kinematical cuts used in an experimental
analysis can remove the FSI eﬀects. Finally we extract elementary (un)polarized diﬀerential cross sections of the nucleon from the photon-deuteron cross sections, and examine how the FSI could distort theextracted elementary cross sections.

Nucleon N(2120) resonance in φp and KΛ(1520) photon production
Ju-Jun Xie, Institute of modern physics, Chinese academy of sciences
We have studied the N(2120) resonance in the γp → K Λ(1520) and γp → φp reactions within theresonance model and the eﬀective Lagrangian approach. It is shown that when the contributions fromthe N (2120) resonance is considered, the current experimental measurement could be well reproduced.
In addition, we also demonstrate that the angular distributions provide direct information of these reactions, which could be useful for the investigation of the N (2120) resonance and may be tested by future
experiments.
+

16:30
DMSB 125

Photoproduction of π − ∆++ , π + ∆0 , and π + n on the proton at Eγ = 1.5−3.0 GeV at LEPS/SPring-8
Hideki Kohri, RCNP, Osaka University
We carry out photoproduction experiments using linearly polarized photon beams with energies of 1.5-3.0
GeV at LEPS/SPring-8. Photoproduction reactions are dominated by isospin rules. In the case of the π∆
photoproduction at forward π angles, the exchange of isospin=1 (π or ρ) in the t-channel is the mostdominant reaction mechanism, which is considered to give a cross section ratio σ(π + ∆0 )/σ(π − ∆++ )of 1/3. Our preliminary experimental ratios are close to 1/3 at very small pi angles and are larger than 1/3
at larger angles. Larger cross section ratios suggest the dd productions are enhanced compared with the uu
productions. The π + n photoproduction, which is caused by the dd productions, is compared with the π∆
photoproduction. These comparisons are important to study N* or ∆* resonances. We are developing apolarized HD target and a large acceptance LEPS2 spectrometer for the near future experiments. Present
status of the developments is reported.

16:50
DMSB 125

Relating CP-violating decays to the neutron EDM
Astrid Hiller Blin, University of Mainz
We use the present upper bound on the neutron electric dipole moment to give an estimate for the upper limit of the CP-violating couplings of the eta(’) to the nucleon. Using this result, we derive constraints on the CP-violating two-pion decays of the eta(’) mesons. Our results (PRD95 (2017), 036022;
arXiv:1612.02276 [hep-ph]) are relevant for the running and planned GlueX and LHCb measurements ofrare meson decays.

29

17:10
DMSB 125NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Nucleon resonances in γp→K∗+ΛFei Huang, University of Chinese Academy of Sciences
The high-precision cross-section data for the reaction γp→K∗+Λ reported by the CLAS Collaboration at
the Thomas Jeﬀerson National Accelerator Facility have been analyzed based on an eﬀective Lagrangian
approach in the tree-level approximation. Apart from the t-channel K, κ, K∗ exchanges, the s-channel
nucleon (N) exchange, the u-channel Λ, Σ, Σ∗(1385) exchanges, and the generalized contact term, thecontributions from the near-threshold nucleon resonances in the s-channel are also taken into account inconstructing the reaction amplitude. It is found that, to achieve a satisfactory description of the diﬀerential
cross section data, at least two nucleon resonances should be included. By including the N(2060)5/2−
resonance, which is responsible for the shape of the angular distribution near the K∗Λ threshold, andone of the N(2000)5/2+, N(2040)3/2+, N(2100)1/2+, N(2120)3/2− and N(2190)7/2− resonances, one
can describe the cross-section data quite well, with the ﬁtted resonance masses and widths compatible
with those advocated by the Particle Data Group. The resulted predictions of the beam, target, and recoil
asymmetries are found to be quite diﬀerent from various ﬁts, indicating the necessity of the spin observable data for γp→K∗+Λ to further pin down the resonance contents and associated parameters in thisreaction.

17:30
DMSB 125

Parallel Session C3
Time: Tuesday, August 22, 2017, 16:00 – 17:50
Room: DMSB 126
Chair: Douglas Hasell
Overview of recent theoretical work on two-photon exchangePeter Blunden, University of Manitoba
In this talk I will given an overview of recent progress in theoretical calculations of two-photon exchange(TPE) eﬀects in elastic electron-proton scattering. This will include a survey of existing models andtheoretical frameworks. TPE eﬀects are relevant for extractions of proton form factors at high Q2 , andof the proton radius at low Q2 . Recent experiments to directly measure hard TPE eﬀects by comparing
positron and electron scattering are being presented in an earlier session, and I will discuss the ﬁndings
from a theoretical perspective.

16:00
DMSB 126

Two-photon exchange: myth and history
Egle Tomasi-Gustafsson, CEA,IRFU, and Université Paris-Saclay
After recalling the arguments for possible excess of two-photon contribution over alpha-counting, model
independent statements about the consequences on the observables will be given. The relevant experimental data are discussed: (polarized and unpolarized) electron and positron elastic scattering on the
proton, as well as annihilation data. Finally a recent reanalysis of the Rosenbluth data in terms of form
factor ratio will be presented.

30

16:30
DMSB 126NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

Two-Photon-Exchange: Future experimental prospects
Jan Bernauer, MITContemporary experiments show a non-zero, but small two-photon-exchange contribution to elastic proton scattering. Unfortunately, this result does not resolve the discrepancy between form factor ratio extractions based on unpolarized and polarized techniques, as a substantially bigger eﬀect is required. However,with a positron beam of higher energy e.g. at Jeﬀerson Lab or DESY, a new generation of experiments
can probe directly the kinematic region where the discrepancy is large. In my talk, I will discuss somepossible scenarios and expected ﬁgure-of-merits for such experiments.

16:50
DMSB 126

Polarized Positron Beam R&D at Jeﬀerson Lab
Joseph Grames, Jeﬀerson Lab
The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the injector of the Continuous
Electron Beam Accelerator Facility demonstrated for the ﬁrst time the eﬃcient transfer of polarizationfrom electrons to positrons via a two-step process: polarized bremsstrahlung radiation is induced bya polarized electron beam in a high-Z target; and then the polarized bremsstrahlung produces polarized
positrons via the pair-production process in the same target. Positron polarization up to 82% was measured
for an initial electron beam momentum of 8.19 MeV/c, limited only by the electron beam polarization.
We will present the results of the PEPPo experiment, and then comment on the challenges and prospects
for providing useful polarized positron beams at the 12 GeV Upgrade of CEBAF.

17:10
DMSB 126

Lepton bremsstrahlung at low energies
Fred Myhrer, University of South Carolina
We will show that at the low energies at PSI the muon proton bremsstrahlung spectrum is no longer peakedin the directions of the traveling muon. The ”peaking approximation” is still very good for electron proton
bremsstrahlung.

17:30
DMSB 126

Parallel Session D3
Time: Tuesday, August 22, 2017, 16:00 – 18:10
Room: DMSB 122
Chair: Elena Santopinto
N* Form Factors based on a Covariant Quark Model
Gilberto Ramalho, LFTC, Universidade Cruzeiro do Sul
We discuss the results from the covariant spectator quark model for some of the well known nucleon
resonances (N*). The form factors and helicity amplitudes are compared with the available data, particularly with the recent Jeﬀerson Lab data at low and high square momentum transfer (Q2 ). The role of thevalence quarks and the meson cloud excitations in the diﬀerent reactions is discussed. We present also
some predictions for N* form factors at large Q2 .

31

16:00
DMSB 122NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

A Light Front Relativistic Quark Model with Running Quark Mass
Volker Burkert, Jeﬀerson Laboratory
I will report on the LF RQM development reported in the Ref. [1] – [6] by the authors. The work is basedon prior research by I. G. Aznauryan and others. In the talk we discuss the model ingredients and thedetermination of the open parameters in ﬁts to the nucleon electromagnetic form factors. We then confront
the predictions of the model to transition form factors of the Δ(1232)3/2+ as well as several excitednucleon states, e.g. the Roper N(1440)1/2+, N(1520)3/2-, N(1535)1/2-. We will also discuss the special
case of N(1675)5/2-, which reveals the nearly pure meson-baryon contributions to the electromagnetictransition to this state from a proton target, although the resonance corresponds to a strong 3-quark state,
as it is revealed in the case of the photo-excitations from a neutron target.
References: [1] Phys.Rev. C95 (2017) 0652. [2] e-print: arXiv:1603.06692 [hep-ph]. [3] Phys.Rev.
C92 (2015), 035211. [4] Phys.Rev. C92 (2015), 015203 . [5] Phys.Rev. C85 (2012), 055202 . [6]Prog.Part.Nucl.Phys. 67 (2012) 1-54.

16:30
DMSB 122

Baryon masses and strangeness suppression in the Unquenched Quark model
Hugo García-Tecocoatzi, INFN sezione di Genova
In this contribution, we brieﬂy analyze the formalism of the unquenched quark model (UQM) and its
application to calculate the mass shifts of ground-state octet and decuplet baryons due to the coupling
to the meson-baryon continuum. We also describe the electro-production of Baryon- Meson states fromproton in the framework of the UQM. Finally, we discuss the strangeness suppression factor within the
UQM, and the theoretical results are in good agreement with the values extracted from CERN and JLabexperiments.

16:50
DMSB 122

Electromagnetic multipole moments of baryons
Alfons Buchmann, Institute for Theoretical Physics, University of Tuebingen
Electromagnetic multipole moments provide important information concerning the charge and magnetization distributions in baryons. In particular, quadrupole and octupole moments reveal interesting details
about their structure, which have not been fully explored.
We calculate the charge quadrupole and magnetic octupole moments of baryons using a group theoretical approach based on broken SU(6) spin-ﬂavor symmetry. The latter is an approximate symmetry of the
QCD Lagrangian that becomes exact in the limit of large number of colors NC . The spin-ﬂavor formalism
includes in addition to the usual one-quark currents, two- and three-quark terms in the electromagnetic
current operator. The two- and three-quark operators provide an eﬀective description of quark-antiquarkand gluon degrees of freedom in baryons, which are essential for a consistent description of baryon structure [1].
We obtain relations between the transition multipole moments to excited states and the electromagnetic
properties of the baryon ground states. Our results are compared to experimental quadrupole and octupoletransition moments, which are extracted from electromagnetic transition amplitudes to excited baryon
states as measured at various electron accelerator facilities [2].
Finally, using various baryon models, we interpret our theoretical results in terms of deviations of thebaryon charge and current distributions from spherical symmetry [1].
References [1] A. J. Buchmann, J. A. Hester, R. F. Lebed, Phys. Rev. D 66, 056002 (2002); A. J.
Buchmann, R. F. Lebed, Phys. Rev. D 67, 016002 (2003); A. J. Buchmann and E. M. Henley, Phys. Rev.
32

17:10
DMSB 122NSTAR 2017 — Book of Abstracts

Tuesday, August 22, 2017

C 63, 015202 (2001); Phys. Rev. D 65, 073017 (2002); Eur. Phys. J. A 35, 267 (2008); Phys. Rev. D
83, 096011 (2011); Few-Body Syst. 55, 749 (2014).
[2] D. Drechsel, S. S. Kamalov, and L. Tiator, Eur. Phys. J. A 34, 69 (2007), http://www.kph.unimainz.de/MAID/; L. Tiator, D. Drechsel, S. S. Kamalov, M. Vanderhaeghen, Eur. Phys. J. ST 198, 141(2011); I. G. Aznauryan and V. D. Burkert, Prog. Part. Nucl. Phys. 67, 1 (2012); C. Patrignani et al.
(Particle Data Group), Chinese Physics C 40, 100001 (2016).

Constituent-quark model with pionic contributions: electromagnetic N → ∆ transition
Ju-Hyun Jung, Universität Graz
We are interested in calculating pion-cloud contributions to the electromagnetic N → ∆ transition form
factors. Starting point is an SU(6) spin-ﬂavor symmetric constituent-quark model with instantaneous
conﬁnement that is augmented by dynamical pions which couple directly to the quarks. This system istreated in a relativistically invariant way within the framework of point-form quantum mechanics using
a multichannel formulation. In order to calculate pion-cloud eﬀects one needs strong πN ∆ and π −∆∆ couplings and form factors as well as electromagnetic N , ∆ and N → ∆ form factors for thebare baryons (i.e. N and ∆ without pionic contributions). In our model we have only four parameters,
the constituent-quark mass, the pion-quark coupling, the mass of the bare N and ∆ (which is the same
due to SU(6) symmetry) and a range parameter for the three-quark wave function of the N and the ∆.
Results for the strong πN N , piN ∆ and π∆∆ couplings and form factors compare surprisingly well withphenomenological ﬁts of those quantities in purely hadronic models. Up till now we have calculated theelectromagnetic form factors of the bare nucleon and the N → ∆ transition with this microscopic model.
Already without pion cloud these quantities compare reasonably well with the data. Although we consider
only S-wave for N and ∆ and have not taken account pion-cloud eﬀects or a D-wave contribution in the
E2
C2∆ up till now, we obtain non-zero ratios REM = M
1 and REM = M 1 . Having collected the necessary
ingredients, it remains to be seen to which extend the electromagnetic N → ∆ transition is aﬀected by
the pion cloud.

17:30
DMSB 122

Mass spectra of singly beauty Ω−b baryon
Zalak Shah, Sardar Vallabhbhai National Institute of Technology
The mass spectra of singly bottom baryon Ω−
b is determined using the Hypercentral Constituent Quark
Model [1]. The conﬁnement potential is assumed in the hyper central co-ordinates as hyper coulomb plus+
power potential. The ground state mΩ− = 6048.8 ± 3.2 MeV with J P = 12 is found experimentally tillb

now [2]. Our calculated mass spectra for Ω−b is obtained by varying potential index ν value from 0.5 to
2.0 for ground and radial excited states while orbital excited states are determined at ν=1.0. Lattice QCD
results and other recent theoretical predicted masses are close to our obtained results [3,4,5]. Using thesemass spectra we plotted Regge trajectories in (n, M 2 ) and (J, M 2 ) planes. The trajectories are useful todetermine unknown J P values of particular states.
[1] Z. Shah, K. Thakkar, A. K. Rai and P. C. Vinodkumar, Eur. Phys. J A 52, 313 (2016); Chin. Phys.
C 40, 123102 (2016). [2] C. Patrignani et. al., Chin. Phys. C 40, 100001 (2016). [3] Z. S. Brown, W.
Detmold, S. Meinel, and K. Orginos, Phys. Rev. D 90, 094507 (2014). [4] S. S. Agaev, K. Azizi, and H.
Sundu, arXiv:1703.07091v1 [hep-ph] (2017). [5] K-W Wei, B. Chen, N Liu, Q. Q. Wang and X-H Guo
arXiv:1609.02512v1 [hep-ph] (2016).

33

17:50
DMSB 122NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Conference Dinner, Top of Carolina
Time: Tuesday, August 22, 2017, 19:00 – 21:00
Room: Capstone Building

Wednesday, August 23, 2017

Parallel Session A4
Time: Wednesday, August 23, 2017, 08:30 – 10:20
Room: DMSB 124
Chair: Dan Carman
Exclusive π − Electroproduction oﬀ the Neutron in Deuterium in the Resonance Region
Ye Tian, Syracuse University
We report the analysis of extracting the exclusive γ n(p) → pπ (p) reaction cross section from deuterium data. The existing γ ∗ n → pπ − event generator is modiﬁed to include the spectator (proton) information based on the CD-Bonn potential to simulate the real data process. With this method, the exclusive
quasi-free process is isolated successfully as demonstrated by the comparison of the spectator momentum
distribution of the simulation with the missing momentum distribution of the data, and the kinematicalﬁnal-state-interaction contribution factor RF SI is extracted directly from the data according to the ratio
between the exclusive quasi-free and full cross sections. The results of this analysis are new the exclusive
and quasi-free cross sections oﬀ neutrons bound in deuterium. Furthermore, the corresponding example
structure functions are extracted from those cross sections as well. The experiment was done in Hall B at
the Thomas Jeﬀerson National Laboratory (JLab) by using the CEBAF Large Acceptance Spectrometer(CLAS) detector, the “e1e” run data oﬀ a liquid deuterium target will provide these ﬁnal results with akinematic coverage for the hadronic invariant mass (W ) up to 1.825 GeV and in the momentum transfer
2(Q2 ) range of 0.4 − 1.0 GeV/c .
∗

−

08:30
DMSB 124

Exclusive π − electroproduction from the neutron in the resonance region
Jixie Zhang, University of Virgina
Pion production from the nucleon is a well-known technique for investigating the resonance. However,data on the neutron are relative scarce when comparing to the proton. In Hall B at Jeﬀerson Lab wehave studied the diﬀerential cross sections for exclusive π − electro-production from the neutron in thereaction of e+d → e0 +π − +p+pr over a broad kinematics range in the BONuS experiment (Barely oﬀ-shell
Nuclear Structure), where pr denotes the recoil proton. The experiment was performed using a radial
time projection chamber (RTPC) and the CEBAF Large Acceptance Spectrometer (CLAS). The RTPC
detector was specially built to detect low energy recoil protons with momenta of 70-250 MeV/c. The
diﬀerential cross sections for D(e, e0 π − p)p have been extracted, with the proton detected either by CLAS
or by the RTPC. The structure functions σT + εσL , σLT and σTT were determined and will be presented incomparison with MAID and SAID models.
34

09:00
DMSB 124NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Investigation of Exclusive π + π − Electroproduction oﬀ the Bound Proton in Deuterium in the Resonance Region with CLAS
Iuliia Skorodumina, University of South Carolina
During the last years, experiments of meson electroproduction on the deuteron target have been inducing
more and more scientiﬁc interest, as they give access to the exclusive reactions oﬀ neutrons and allow tojudge the inﬂuence of the nuclear medium on the reaction processes. Beside that, these experiments oﬀer
a great opportunity to study the initial and ﬁnal state interactions for diﬀerent exclusive channels as wellas the eﬀects of the Fermi motion of nucleons. Being the lightest and most weakly bound nucleus, thedeuteron is the best target to start these eﬀorts.
The main purpose of the research I am currently carrying out is to provide new information on exclusive
charged double pion electroproduction oﬀ the proton bound in deuteron via the analysis of CLAS experimental data. The research aims to provide for the ﬁrst time a set of integrated and one-fold diﬀerential
cross sections of this exclusive channel in the quasi-free regime. The extracted cross sections will becompared with the corresponding cross sections of the same reaction oﬀ the free proton, which have been
recently extracted from the same run period (that included both a hydrogen and deuterium target run in
the same experimental conﬁguration) [G. Fedotov et al., Analysis report on the ep → e0 p0 π + π − reactionin the CLAS detector with a 2.039 GeV beam for 0.4 GeV2 < Q2 < 1.0 GeV2 and 1.3 GeV < W <1.825 GeV. CLAS-ANALYSIS-NOTE-2017-101]. The direct comparison of these two sets of cross sections obtained under the almost identical conditions will hence provide the experimentally best possible
opportunity to investigate the diﬀerences and alterations that occur in the exclusive reaction oﬀ boundproton in comparison with that oﬀ the free proton. This comparison will also allow us to understand theinﬂuence of Fermi motion and ﬁnal state interactions on the cross sections better.
In the talk I am going to introduce the preliminary integrated and diﬀerential cross sections of theγv p(n) → p0 (n0 )π + π − reaction and their comparison with the corresponding cross-sections oﬀ thefree proton. Beside that, some details of the data analysis as well as some speciﬁc issues intrinsic for the
deuteron target experiment will be presented.

09:20
DMSB 124

Fermi-unsmearing: A Monte Carlo method to correct for Fermi-motion of a target nucleon.
Gary Hollis, University of South Carolina
For many reasons, especially the measurement of cross sections oﬀ the neutron, scattering experiments
may use bound nucleons as targets. However, the bound nucleon’s momentum is not negligible, and thenucleon is said to have Fermi-motion. For quasi-free scattering, when all ﬁnal state particles besides the
spectator(s) are measured, the initial momentum can be inferred and the cross section can be extracted.
However, whenever it is impractical to reconstruct the initial momentum of the target nucleon, the current
approach is to ignore the motion of the target nucleon and hence to accept a distortion in the cross section
known as Fermi-smearing. This talk discusses the development of a Monte Carlo method that removes
this distortion eﬀect, resulting in a realistic W-dependence of the cross section.

09:40
DMSB 124

Determination of the Polarization Observables Cx , Cz , and Py for the Quasi-Free Mechanism in−→→
the reaction −γ d → K+ Λ nTongtong Cao, Hampton University
−
→
−
→
→
→
Besides the reaction −γ p → K + Λ , the Quasi-Free (QF) mechanism in the reaction −γ d → K+ Λ n
35

10:00
DMSB 124NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017provides an alternative means to study photoproduction of strangeness oﬀ the proton leading to the K + Λstate. In this work, we determine the polarization transfers, Cx and Cz , from circularly polarized photons−→→
to the Λ, and the hyperon recoil polarization, Py , for the QF mechanism in the reaction −γ d → K + Λ n forEγ between 0.9−2.6 GeV and cosθKCM between -1−1. The observables are obtained from data takenwith the CLAS detector at the Thomas Jeﬀerson National Accelerator Facility during the E06−103 (g13)→experiment. The extracted observables are compared to published CLAS results on the reaction −γp→→+−K Λ . In the talk, eﬀects of the Fermi momentum of the bound proton on the extracted observables will
be discussed. This work is funded in part by the U.S. NSF under grant PHY-125782.

Parallel Session B4
Time: Wednesday, August 23, 2017, 08:30 – 10:20
Room: DMSB 125
Chair: Craig Roberts
Structure of the Orbital Excited N* from SDE
Adnan Bashir, University of Michoacan
I present advances towards the calculation of the N → N ∗ (1535) Transition Form Factor throughSchwinger-Dyson equations.

08:30
DMSB 125

A process-independent QCD eﬀective charge: a main ingredient for a further computation of
nucleon-to-resonances transitions
José Rodríguez-Quintero, University of Huelva & CAFPE (U. Granada)
We have recently uniﬁed two widely diﬀerent approaches to understanding the infrared behaviour ofquantum chromodynamics (QCD), one essentially phenomenological, based on data, and the other computational, realised via quantum ﬁeld equations in the continuum theory. Using the latter, we explained
and calculated a process-independent running-coupling for QCD, a new type of eﬀective charge that is ananalogue of the Gell-Mann–Low eﬀective charge in quantum electrodynamics. This process-independent
charge will necessarily be a noteworthy piece of information for the eﬀort to derive the nucleon-toresonances transitions and, reversely, the measurements of these transitions will be crucial for the practical
validation of that charge.

09:00
DMSB 125

Aspects of Nucleon Parton Structure from a DSE Implementation of QCD
Peter Tandy, Kent State University
The parton structure of the nucleon is investigated in an approach based upon QCD’s Dyson-Schwinger
equations. The method accommodates a variety of QCD’s dynamical outcomes including: the runningmass of quark propagators and formation of non-pointlike di-quark correlations. The method can produce
a large number of moments, and thus complements lattice-QCD which is presently reliable for about 3
moments only. All needed elements, including the nucleon wave function solution from a covariant Faddeev equation, are encoded in spectral-type representations in the Nakanishi style to facilitate Feynman

36

09:20
DMSB 125NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

integral procedures and allow insight into key underlying mechanisms. Results will be presented for spinindependent PDFs arising from a truncation to allow only scalar di-quark correlations. initial explorationsof axial-vector di-quark correlations and extension to TMDs may be discussed if results are available.

The QCD running coupling at all scales and the connection between the proton mass and ΛM S
Alexandre Deur, Jeﬀerson Lab
The running coupling αs (Q ) sets the strength of QCD as a function of the momentum transfer Q. Knowing the Q2 -dependence of αs is necessary to describe hadronic interactions at both large and short distances. At short distances, the Q2 -dependence is speciﬁed by perturbative QCD and its renormalizationgroup equation. It is well known, with the 5-loops calculations now available. Since QCD is nearly
conformal at small distances, the strength of the Q2 -dependence is set by a non-perturbative parameter,
usually ΛQCD . In this talk, we will show the prediction of holographic-QCD for αs at low Q2 , and compare it to experimental data and to other non-perturbative calculations. Matching the high and low Q2
regimes of αs (Q2 ) allows us to relate ΛQCD to the holographic-QCD conﬁnement parameter κ, thereby
establishing an explicit relation between the physics of conﬁnement and the dynamical interactions ofquarks and gluons at short distances. This provides an analytic connection between hadronic masses andΛQCD .
2

09:40
DMSB 125

Disentanglement of Electromagnetic Baryon Properties
Daniel Sadasivan, George Washington University
Through recent advances in experimental techniques, the precise extraction of the spectrum of baryonic
resonances and their properties becomes possible. Helicity couplings at the resonance pole are fundamental parameters describing the electromagnetic properties of resonances and enabling the comparisonof theoretical models with data. We have extracted them from experiments carried out at Jeﬀerson Lab
and other facilities using a multipole analysis within the Julich-Bonn framework. Special attention has
been paid to the uncertainties and correlations of helicity couplings. Using the world data on the reaction γp → ηp, we have calculated, for the ﬁrst time, the covariance matrix. Our results are usefulin several ways. They quantify uncertainties but also correlations of helicity couplings. Second, they
can tell us quantitatively how useful a given polarization measurement is. Third, they can tell us how
the measurement of a new observable would constrain and disentangle the resonance properties which
could be helpful in the design of new experiments. Finally, on the subject of the missing resonance problem, model selection techniques and statistical tests allow us to quantify the signiﬁcance of whether aresonance exists.

Parallel Session C4
Time: Wednesday, August 23, 2017, 08:30 – 10:20
Room: DMSB 126
Chair: Eulogio Oset

37

10:00
DMSB 125NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

N to Δ transition: recent results and prospects
Nikos Sparveris, Temple University
The study of the N to Δ transition has been the subject of an intense scientiﬁc interest for more than two
decades. The pion electroproduction and VCS channels of the transition provide access to the N to Δ
transition amplitudes and oﬀer a path for the exploration of the dynamics associated with the presenceof non-spherical angular momentum amplitudes in hadrons. At the same time the VCS channel provides
access to another set of fundamental properties of the nucleon, the Generalized Polarizabilities. Recent
results from JLab and MAMI will be presented and future prospects will be discussed.

08:30
DMSB 126

Nucleon and Delta structure results from lattice QCD
Giannis Koutsou, The Cyprus Institute
Recent nucleon structure results will be presented from lattice QCD simulations at physical or near physical quark mass. We will also present results on the electromagnetic and axial delta and nucleon to deltatransition, as well as an outlook on the study of resonances on the lattice.

09:00
DMSB 126

The Role of the ∆(1232)-Resonance in the (Muonic) Hydrogen Spectrum
Franziska Hagelstein, JGU Mainz
The electromagnetic excitation of the ∆(1232) plays an appreciable role in the Lamb shift and hyperﬁne
structure of muonic hydrogen. Its eﬀect appears at the order α5 , together with other proton-polarizability
contributions, and therefore is subleading with respect to the proton charge radius contribution which isof order α4 , see e.g. [1]. We use the large-Nc relations for the nucleon-to-delta transition form factors [2]to compute the ∆(1232) contribution. We show that the hyperﬁne splitting is dominated by the magnetic
N → ∆ transition and present a simple formula, involving the nucleon Pauli form factor, setting a lower
bound on the absolute eﬀect of the ∆-resonance. The planned PSI measurement of the ground-state
hyperﬁne splitting in muonic hydrogen will require at least a factor 10 improvement in precision of thetheory predictions of proton polarizability contributions [3].
[1] F. Hagelstein, et al., Prog. Part. Nucl. Phys. 88 (2016) 29-97. [2] V. Pascalutsa and M. Vanderhaeghen, Phys. Rev. D 76 (2007) 111501. [3] R. Pohl, et al., physics.atom-ph/1609.03440.

09:20
DMSB 126

The VCS-Δ experiment at MAMI
Michael Paolone, Temple University
High precision measurements of the Virtual Compton Scattering reaction at the ﬁrst nucleon resonancehave been performed at the MAMI Microtron at Mainz. The experiment focuses on the study of theelectric Generalized Polarizability of the proton and on the ﬁrst extraction of the Coulomb quadrupoletransition amplitude through the photon excitation channel. In this talk details of the experiment, thestatus of the data analysis, and preliminary results will be presented.

38

09:40
DMSB 126NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Virtual Compton Scattering measurements in Hall C at JLabMark Jones, Jeﬀerson Lab
The Generalized Polarizabilities, GPs, are fundamental quantities of the nucleon and as such they are
extremely valuable for a deeper and more complete understanding of the nucleon structure. The GPs canbe accessed experimentally through measurements of the Virtual Compton Scattering reaction. They canbe seen as Fourier transforms of local polarization densities (electric, magnetic, and spin) and therefore
are a probe of the nucleon dynamics, allowing us, e.g., to study the role of the pion cloud and quark core
contributions to the nucleon GPs at various length scales.
A new experiment in Hall C at JLab will explore the proton GPs with an unprecedented high precision. The unique capabilities of the experimental setup, namely the high resolution of the spectrometers
combined with the ability to place the spectrometers in very small angles, will provide high precision
measurements of the VCS reaction in a kinematic region where the GPs are changing rapidly and exhibita puzzling dependence with Q2 . The upcoming measurements will explore the mechanisms responsible
for the non-trivial Q2 dependence of the electric GP and will signiﬁcantly improve the knowledge of themagnetic GP.

10:00
DMSB 126

Break (Coﬀee / Refreshments)
Time: Wednesday, August 23, 2017, 10:20 – 10:50
Room: Sonoco Pavilion

Parallel Session A5
Time: Wednesday, August 23, 2017, 10:50 – 12:40
Room: DMSB 124
Chair: Victor Mokeev
Extracting Resonance Parameters from Exclusive Electroproduction oﬀ Protons at CLAS
Kijun Park, Jeﬀerson Lab
The measurement of the excited nucleon states play a crucial role for the insight of the structure of thenucleon. Such a N ∗ spectrum contains the direct information of the underlying degree of freedom of thenucleon. In particular, the exclusive meson electroproduction oﬀ protons is a powerful tool to probe theeﬀective degrees of freedom in excited nucleon states at the varying distance scale where the transition
from the contributions of both quark-core and meson-baryon cloud to the quark-core dominance. During
the past decade, the CLAS collaboration has executed a broad experimental program to study the excitedstates of the proton using polarized electron beam and both polarized and unpolarized proton targets. The
measurements covered a broad kinematic range in the invariant mass W and photon virtuality Q2 withnearly full coverage in polar and azimuthal angles in the hadronic CM system. As results, several nucleon
resonance states in particular from near pion threshold to W < 2 GeV have been explored. These include
+
+
−
−
−
the axial form factors, ∆(1232) 32 , N (1440) 12 , N (1520) 32 , N (1535) 12 as well as the N (1675) 52 ,++N (1680) 52 , and N (1710) 12 states. I will brieﬂy discuss these resonance states as well as DIS resultsfrom the single charged pion electroproduction data at CLAS.

39

10:50
DMSB 124NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Exclusive π 0 electroproduction in the resonance region.
Nikolay Markov, University of Connecticut
The exclusive electroproduction process ep → e p π was measured in the range of the photon virtuality
Q2 = 0.4−1.0 GeV2 , and the invariant mass range of the pπ 0 system of W = 1.1−1.8 GeV. For the ﬁrst
time, these kinematics are covered in exclusive π 0 electroproduction oﬀ the protons with nearly complete
angular coverage in the pπ 0 center of mass system with extremely high statistics. Cross section and beam0
spin asymmetry were measured and structure functions σT + σL , σT T , σLT and σLT
were extracted∗
via the ﬁtting the φ dependance. Comparison between the experimental results on exclusive structure
functions σT +σL , σT T , σLT and evaluations within the JLAB/YerPHY unitary model revealed the data
sensitivity to the variations of the electroexcitation amplitudes for the nucleon resonances N (1650)1/2− ,N (1685)5/2+ , and ∆(1700)3/2− . Combined studies of π + n and π 0 p electroproduction oﬀ protons datafrom CLAS at W >1.6 GeV will provide the ﬁrst results on the high lying N* and ∆* electrocouplingsat Q2 < 1.0 GeV 2 for all excited nucleons with substantial decays to the N π ﬁnal states. These newexperimental data will extend the insight into the complex interplay between inner quark core and outermeson-baryon cloud in the structure of nucleon resonances with masses above 1.6 GeV.
0 0 0

11:20
DMSB 124

Response Functions from Exclusive Measurements of ω Meson Electroproduction oﬀ the Proton
Evan Phelps, University of South Carolina
A central goal of hadronic physics is to understand the structure of hadrons in terms of Quantum Chromodynamic’s (QCD’s) current quarks and gluons and to connect the observable properties of hadrons to the
dynamical content of QCD. This endeavor entails knowledge of the baryon spectrum, the proton form factor, and transition form factors. Photoproduction experiments are excellent probes of the excited baryon
spectrum, and electroproduction experiments additionally aﬀord access to the proton and transition form
factors. Among electroproduction channels, ω electroproduction provides a discriminating probe of thehigh-lying resonance region due to the meson’s high mass, narrow decay width, and isoscalar nature that
restricts it to isospin-1/2 resonance couplings. Using data collected by Jeﬀerson Lab’s CLAS detector
during run periods E1F and E16, with beam energies close to 6 GeV, exclusive ω electroproduction oﬀ
the proton was studied via the three-pion decay channel, ep → eωp → eπ + π − π 0 p. Diﬀerential crosssections were measured for W = [1.72, 2.60) GeV, Q2 = [1.85, 5.15) GeV2 , and over the full solidangular range. Response functions RT + L RL , RT T , and RT L were extracted in order to be utilized
in the extraction of resonance parameters within single-channel or dynamical coupled channel analyses.
Results, conclusions, and prospects will be reported.

11:40
DMSB 124

Measurement of New Observables from the π + π − p Electroproduction oﬀ the Proton
Arjun Trivedi, University of South Carolina
A key objective of the N* program is to measure the resonance transition form factors that contain information needed to explore the distance-dependence description of the interaction of a probe with thenucleon resulting in its excitation to one of its various resonance states. These resonance transition form
factors are sensitive to the underlying degrees of freedom of the nucleon and their dynamics while being
conﬁned within the nucleon, and therefore serve to understand the emergent complexity of the Universeat the most fundamental level. Experimental observables from single- and double-charged electroproduction channels serve as dominant sources for the extraction of these form factors in the two dimensionallandscape spanned by the variables Q2 and W , which map out the space-time scale of the degrees of
40

12:00
DMSB 124NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

freedom and their dynamics during the interaction as well as the range of possible excitations of the nucleon, respectively. For the ﬁrst time, in hitherto unexplored regions of Q2 and W , observables in the
double-charged channel that are sensitive to the polarization of the virtual photon are measured using
the π + π − p reaction channel. I will present preliminary measurements for these new observables for
2 GeV 2 < Q2 < 5 GeV 2 and 1.400 GeV < W < 2.125 GeV using data collected at theexperimental facility of Jeﬀerson Laboratory, preceded by an introduction to these observables and therelevant details of the experimental analysis.

New results on γv p → p0 π + π − cross sections in the resonance region with CLAS
Gleb Fedotov, Ohio University
The new results on the integral and single-diﬀerential cross sections of the π π electroproduction oﬀ
protons measured in the invariant mass range of the ﬁnal hadron system W from 1.3 GeV to 1.825 GeV
and at photon virtualities Q2 from 0.4 GeV2 to 1.0 GeV2 will be reported. These measurements have
expanded the range of covered photon virtualities towards smaller values in comparison with the previous
CLAS experiments and allowed to extract the cross sections in 0.05-GeV2 -ﬁne Q2 -bins, which is a factorof six narrower than previously achieved [M. Ripani et al. CLAS Collaboration, Phys. Rev. Lett. 91,
022002 (2003).].
The extracted cross sections were compared with the prediction of recently developed TWOPEG [Iu.
Skorodumina et al. arXiv:1703.08081 (2017)] event generator which is based on JM model [V.I.Mokeev,
V.D.Burkert et al, Phys. Rev. C93, 025206 (2016)] ﬁt to the previously available data and a good agreement was revealed. The resonant contribution to the cross section was estimated with the direct use of
the phenomenological reaction model (JM) and was found to be signiﬁcant.
The studies of the N* electroexcitation amplitudes, also known as electrocouplings, at various photon
virtualities represent an important part of the scientiﬁc program with the CLAS and CLAS12 detectors
at Jeﬀerson Lab. It is expected that the future detailed analysis of the extracted cross sections within
JM model will improve the knowledge on γv pN* electrocouplings for exited states with masses above
1.6 GeV, since many of them decay preferentially to the Nππ ﬁnal state. For low-laying resonances thisanalysis will oﬀer a valuable cross-check of the obtained resonance parameters via their comparison with
the independent results from Nπ exclusive channel.
+ −

12:20
DMSB 124

Parallel Session B5
Time: Wednesday, August 23, 2017, 10:50 – 12:20
Room: DMSB 125
Chair: Eugene Pasyuk
Exclusive Meson Photoproduction oﬀ Bound Nucleons
Igor Strakovsky, The George Washington University
An overview of the GW SAID group eﬀort to analyze pion photoproduction on the neutron-target will
be given. The disentangling of the isoscalar and isovector EM couplings of N∗ and Δ∗ resonances does
require compatible data on both proton and neutron targets. The ﬁnal-state interactions play a critical rolein the state-of-the-art analysis in extraction of the γn → πN data from the deuteron target experiments.
Then resonance couplings determined by the SAID PWA technique are compared to previous ﬁndings.

41

10:50
DMSB 125NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

The neutron program is an important component of the current JLab, MAMI-C, SPring-8, ELSA, and
ELPH studies.

Evaluating Polarization Data
Dave Ireland, University of Glasgow
There is a large amount of polarization observable data that has been collected in recent years, from avariety of channels and from diﬀerent experiments. If this data is going to prove ultimately useful in the
study of N ? resonances, and other physics topics, it is imperative that it be consistent, to avoid pathologies
in the ﬁtting of models. Taking an example of KΛ photoproduction, a method will be demonstrated that
ensures data representing a set of diﬀerent observables, which could have been extracted independently
from diﬀerent experiments, are guaranteed to be self-consistent.

11:20
DMSB 125

CLAS12 RICH: New hybrid geometry for strangeness studies.
Giovanni Angelini, The George Washington University
The JLAB CLAS12 detector will provide a world-leading facility for the study of electron-nucleon scattering. The experiment will accumulate data with unprecedented statistical accuracy, thanks to its 12 GeVpolarized electron beam and its luminosity, the availability of unpolarized as well as polarized hydrogenand nuclear target, and its wide kinematic coverage. The CLAS12 physics program is very broad andincludes studies on the meson spectroscopy with quasi-real photoproduction in a large variety of ﬁnal
states. The particle identiﬁcation will be complemented by a Ring Imaging Cherenkov Detector (RICH),
that will provide separation of kaons from protons and pions in the momentum range between 3-8 GeV/callowing the study of double and triple strange baryons. In this talk, we will focus on the new technologies developed for the RICH, especially on the complex mirror system, that thanks to a hybrid geometry
allow reducing the photo-detection area. The expected performance of the detector will be presented as
well.

11:40
DMSB 125

Photoproduction of π 0 π ± Pairs oﬀ Nucleons
Natalie Walford, University BaselPhotoproduction of meson pairs oﬀ (quasi-) free nucleons is important to investigate the excitation spectrum of the nucleon for low energy QCD, in particular for excited states which decay predominantly via
intermediate excited states to the ground state. Quasi-free production of such pairs oﬀ heavier nuclei
also ﬁgures prominently in the study of the in-medium properties of nucleon resonances. Double meson
production channels make the largest contribution to the second resonance bump of the nucleon, which
disappears for photoproduction oﬀ nucleons bound in nuclei. The special interest in the mixed charged
channels π 0 π ± is related to the contribution of the ρ-meson. This decay is forbidden for the π 0 π 0 ﬁnal
state due to isospin conservation. The coupling to a ρ could induce substantial in-medium eﬀects whenthe ρ spectral function itself is modiﬁed in the medium. In the present work, production of π 0 π ± pairs oﬀ
liquid deuterium and liquid hydrogen was analysed using data taken at MAMI with the A2 experiment
as a starting point for a detailed investigation of this channel for nuclear targets.

42

12:00
DMSB 125NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Parallel Session C5
Time: Wednesday, August 23, 2017, 10:50 – 12:40
Room: DMSB 126
Chair: Reinhard Beck
Bridging Time-Like and Space-Like N* Form Factors
Philip Cole, Lamar University
The study of electromagnetic transitions opens a window into the very nature of the strong interaction.
And, indeed, such a study of how a ground-state nucleon transitions to an excited state, over a broad rangeof q2, will provide keen insight into the evolution of how dynamically-generated masses emerge from theasymptotically-free, nearly massless quarks of perturbative QCD as well as provide information on the
ancillary eﬀects from the meson-baryon cloud. The space-like (q2<0) region has been explored more
intensively, particularly at JLab, but eﬀorts have also begun in studying the time-like (q2>0) region at
GSI. We are living in exciting times whereby near-future prospects exist in extracting high-quality data inboth the space-like and time-like regimes (JLab12 and FAIR, for example). The recent ECT* workshop,
entitled space-like and time-like electromagnetic baryonic transitions, brought together several disparate
communities of experimentalists and theorists. The goal and purpose of this workshop was to make thevery ﬁrst steps towards a much needed consistent description spanning the two kinematical regimes in q2.
The discussions included photoproduction measurements (ELSA, JLab, LEPS, and MAMI), wherein theq2=0 point anchors the connection between space-like and time-like regions and meson-beam data (GSI,
FAIR, and J-PARC) and amply complements the requisite information for baryon spectroscopy. This talkwill present the outcomes from this ECT* workshop and will set the stage for the dedicated NSTAR 2017
parallel session entitled baryon structure through meson electroproduction, transition form factors, andtime-like form factors.

10:50
DMSB 126

Studying time-like electromagnetic baryonic transitions with HADES in π-N reactions
Béatrice Ramstein, Institut de Physique Nucléaire d’Orsay
A dedicated programme to study electromagnetic baryonic transitions in the time-like region has started
using the pion beam [1] and the HADES (High Acceptance Di-Electron Spectrometer) set-up [2] at GSI.
Combined measurements of hadronic and dielectron ﬁnal states have been performed for the ﬁrst time inπ-N reactions, using polyethylene and carbon targets. Diﬀerential cross-sections of the exclusive channels with two pions in the ﬁnal state (π − π + n, π 0 π − p) were obtained in the second resonance region
with an unprecedented statistics. These new data were included in the partial wave analysis (PWA) of theBonn-Gatchina group [3] together with the world data from pion and photon beam facilities. The obtained
solution provides the excitation function of the two-pion production in photo- and pion- induced reactions around the pole of the N(1520)D13 resonance and of its decomposition into the diﬀerent resonant,non-resonant and ρ contributions.
Results for the exclusive ne+ e− production will be compared to various model calculations. In addition,
the extraction of the ρ contribution in the two-pion production channels are used to investigate the validityof the Vector Dominance Model for baryon transitions. The angular distributions of the leptons, whichcontain additional information on the electromagnetic structure of the diﬀerent transitions, will also be
discussed.

43

11:20
DMSB 126NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

The prospects for future experiments where the third resonance region will be investigated will also bepresented.
[1] P. Salabura, J. Stroth, L. Fabbietti (HADES), Nucl. Phys. News 25 (2015) 22. [2] G. Agakishiev etal. (HADES), Eur. Phys. J. A 41 (2009) 243. [3] A.V. Anisovich, E. Klempt, A.V. Sarantsev, U. Thoma,
Eur. Phys. J. A 24 (2005) 111.

Hyperon-photon physics
Stefan Leupold, Uppsala University
In the last decades a lot of progress has been made in the understanding of the electromagnetic form factorsof the nucleons and transition form factors of the nucleon to baryonic resonances. This information canbe complemented and deeper examined by determining the corresponding quantities for hyperons. Dalitz
decays of hyperons into lighter hyperons and a lepton pair provide access to low-energy transition form
factors. On the theory side one can use dispersion theory to relate these form factors to the pion vector
form factor and pion-hyperon scattering amplitudes. The latter can be addressed with chiral perturbation
theory including decuplet states [1]. In my talk I will report on these ongoing theory developments.
[1] C. Granados, S. Leupold and E. Perotti, The electromagnetic Sigma-to-Lambda hyperon transition
form factors at low energies, Eur. Phys. J. A 53, 117 (2017).

11:40
DMSB 126

Polarization and dilepton anisotropy in pion-nucleon collisions
Miklós Zétényi, Wigner RCP, Budapest
We study hadronic polarization and the related anisotropy of the dilepton angular distribution for thereaction πN → N e+ e− . We employ consistent eﬀective interactions for baryon resonances up to spin-5/2
to compute their contribution to the anisotropy coeﬃcient. We show that the spin and parity of theintermediate baryon resonance is reﬂected in the angular dependence of the anisotropy coeﬃcient. We
present results for the anisotropy coeﬃcient including the N(1520) and N(1440) resonances, which areessential at the collision energy of the recent data obtained by the HADES collaboration on this reaction.
We conclude that the anisotropy coeﬃcient provides useful constraints for unravelling the resonancecontributions to this process.

12:00
DMSB 126First Results from the BGO-OD Experiment at ELSA
Hartmut Schmieden, Physics Institute (PI), University of Bonn
BGO-OD is a new experiment at the University of Bonn‘s ELSA accelerator facility. It consists of a highly
segmented BGO calorimeter at central angles combined with an Open Dipole magnetic spectrometer inforward directions. The setup is ideal for meson photoproduction at low momentum transfers, in particularin KY photoproduction. It allows to investigate threshold eﬀects and the role of (vector-) meson – baryon
interactions. Data taking has started and ﬁrst preliminary results will be shown.

Lunch Break

44

12:20
DMSB 126NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Time: Wednesday, August 23, 2017, 12:40 – 14:00

General Session P7
Time: Wednesday, August 23, 2017, 14:00 – 16:00
Room: DMSB 123
Chair: Fred Myhrer
Resonance Parameters from Strangeness Photo- and Electroproduction
Jan Ryckebusch, Ghent University
We lay out a framework that can be used to obtain estimates of the possible impact of (combinations)of polarization measurements in strangeness photoproduction from the nucleon. To this end, we introduce a geometrical measure to quantify the distance between models for strangeness photoproductionin amplitude space. Experimental observables, with ﬁnite accuracy, map to probability distributions in
amplitude space, and the characteristic width scale of such distributions needs to be smaller than the
distance between models if the observable data are going to be useful. We therefore also introduce amethod for evaluating probability distributions in amplitude space that arise as a result of one or moremeasurements, and show how one can use this to determine what further polarization measurements aregoing to be necessary to be able to discriminate among models.

14:00
DMSB 123

Nucleon Excited States from Lattice QCD and Hamiltonian Eﬀective Field Theory
Jiajun Wu, University of Adelaide
An approach for relating the nucleon excited states extracted from lattice QCD and the nucleon resonances of experimental data has been developed using the Hamiltonian eﬀective ﬁeld theory (HEFT)
method. By formulating HEFT in the ﬁnite volume of the lattice, the eigenstates of the Hamiltonianmodel can be related to the energy eigenstates observed in Lattice simulations. By taking the inﬁnitevolume limit of HEFT, information from the lattice is linked to experiment. The approach opens a new
window for the study of experimentally-observed resonances from the ﬁrst principles of lattice QCD calculations. With the Hamiltonian approach, one not only describes the spectra of lattice-QCD eigenstates
through the eigenvalues of the ﬁnite-volume Hamiltonian matrix, but one also learns the composition of
the lattice-QCD eigenstates via the eigenvectors of the Hamiltonian matrix. One learns the compositionof the states in terms of the meson-baryon basis states considered in formulating the eﬀective ﬁeld theory.
One also learns the composition of the resonances observed in Nature. In this presentation, I will focus on
recent breakthroughs in our understanding of the structure of the N*(1535), N*(1440) and Lambda(1405)
resonances using this method.

14:30
DMSB 123

Time-Like Baryon Transitions in Hadroproduction
Béatrice Ramstein, Institut de Physique Nucléaire d’Orsay
Originally designed to study medium eﬀects in e+ e− production in heavy-ion reactions in the SIS-18
energy range (1-3 GeV/nucleon), the High Acceptance Di-Electron Spectrometer (HADES) [1] installedat GSI is a versatile detector. Its excellent particle identiﬁcation capabilities allowed for a systematicinvestigation of dielectron, strange particles and pion production in proton, deuteron or heavy-ion induced
45

15:00
DMSB 123NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

reactions on proton or nucleus. The obtained dilepton spectra measured at various beam energies show
important contributions from baryon resonance decays (R → N e+ e− ) and a strong inﬂuence of theintermediate vector mesons (ρ/ω/φ) in the corresponding time-like electromagnetic form factors.
In order to directly access such transitions, HADES has started a dedicated pion-nucleon programme [2].
For the ﬁrst time, combined measurements of hadronic and dielectron ﬁnal states have been performedin π-N reactions in the second resonance region, using polyethylene and carbon targets. While providing
new determinations of the baryon-meson couplings, the results allow to investigate the validity of the
Vector Dominance Model for baryon transitions and the helicity structure of the time like electromagnetic
baryon transitions, paving the way for more precise future measurements.
The results of the HADES collaboration obtained with proton and pion beams will be presented, as wellas prospects for HADES measurements at SIS-18 in the near future and later at SIS-100 (FAIR).
[1] G. Agakishiev et al. (HADES), Eur. Phys. J. A 41 (2009) 243. [2] P. Salabura, J. Stroth, L. Fabbietti(HADES), Nucl. Phys. News 25 (2015) 22.

CLAS N* Excitation Results from Pion and Kaon Electroproduction
Daniel Carman, JLab
The study of the structure of excited nucleon N states employing the electroproduction of exclusive
reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The
electrocouplings of N ∗ states in the mass range below W =1.8 GeV have been determined from analysesof CLAS πN , ηN , and ππN data at four momentum transfers Q2 up to 5 GeV2 . This work has madeit clear that consistent results from independent analyses of several exclusive channels with diﬀerent
couplings and non-resonant backgrounds but the same N ∗ electro-excitation amplitudes, is essential tohave conﬁdence in the extracted results. In terms of hadronic couplings, many high-lying N ∗ states
preferentially decay through the ππN channel instead of πN . Therefore, data from the KY channels
already measured with CLAS will be crucial to provide an independent analysis to compare the extracted
electrocouplings for the high-lying N ∗ states against those determined from the πN and ππN channels.
These comparisons await the develop of suitable KY reaction models. Starting later this year, a program
to study the structure of N ∗ states in various exclusive electroproduction channels using the new CLAS12
spectrometer will get underway. These studies will probe the structure of these states in the mass range
up to W =3 GeV and Q2 up to 12 GeV2 , thus providing a means to access N ∗ structure information
spanning a broad regime encompassing both low and high energy degrees of freedom.
∗

15:30
DMSB 123

Break (Coﬀee / Refreshments)
Time: Wednesday, August 23, 2017, 16:00 – 16:30
Room: Sonoco Pavilion

General Session P8
Time: Wednesday, August 23, 2017, 16:30 – 18:00
Room: DMSB 123
Chair: Yordanka Ilieva
Exclusive Meson Electroproduction oﬀ Bound Nucleons
Toru Sato, Osaka University

16:30
DMSB 123

46

NSTAR 2017 — Book of Abstracts

Wednesday, August 23, 2017

Excited nucleon states are characterized by the poles and residues of the meson production amplitudes.
In this talk we brieﬂy discuss the the ANL-Osaka dynamical coupled channel (DCC) approach to analyze
meson production reactions and the resonance parameters extracted from the amplitudes within the DCC
model.
The isospin structure of those resonance parameters will clarify the structure of resonances together withpossible non-trivial eﬀects of meson production mechanism. We then discuss the electroweak pion production reactions on deuteron and possible eﬀect of ﬁnal state interaction when extracting neutron amplitudes.

N* Structure from Constituent Quark Models
Elena Santopinto, INFN Genova
A review of quark model theoretical results on electromagnetic transition form factors of the N* resonances will be presented and discussed in comparison with the experimental data

17:00
DMSB 123

Baryons in Medium
Steﬀen Strauch, University of South Carolina
Many QCD-based models predict changes of the nucleon wave functions in the nuclear medium, including
observable changes in the nucleon structure functions and electromagnetic form factors. While thesein-medium form factors are not observable, they provide a natural explanation of a variety of experimental
results. I will review some of these ﬁndings and discuss upcoming experiments.

Concluding Remarks — NSTAR 2019 will be held in Bonn
Time: Wednesday, August 23, 2017, 18:00 – 18:30
Room: DMSB 123

47

17:30
DMSB 123