Quasi-free One-proton Knockout
Reactions along the Oxygen Isotopic
Chain
Leyla Atar1
T. Aumann1, C. Bertulani2, S. Paschalis3
for R3B Collaboration
1. TU Darmstadt
2. Texas A&M University-Commerce, USA
3. University of York, UK

January 17, 2017

Outline

Quasi-free (p,2p) on Oxygen Isotopes- Introduction- Experimental Setup- Analysis Results
Fission Reactions via Quasi-free (p,2p)
Summary & Outlook

Single-Particle Strength
IPM: Nucleons are single particles moving independently in a mean field created byall nucleons.
(e,e'p) reactions at NIKHEFReduction factor
R = σexp/σIPM
relative to the IPM!
R

30-40% deviation of the single-particle
strength relative to the IPM
Correlations:
not included in the IPM
such as short-range and tensor,
long-range→ configuration mixing→ high momenta

Leyla Atar

H. Dickhoff, C. Barbieri Prog. Nucl. Phys. 52, 377 (2004)
NIKHEF data: L. Lapikas Nucl. Phys. A553, 297c (1993)

NIKHEF data is limited to stable nuclei
and valence proton states.

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.20172

Quenching of Single-Particle Strength

weakly boundstrongly bound

Isospin dependency of singleparticle strength in asymmetricsystems?
Quenching of single-particle
strength in strongly bound states?
→ origin unclear
Nucleon removal reactions withexotic beams at intermediate
energies are limited to surface
localized reactions→ Reaction mechanism?
→ Missing correlations in SM?
Leyla Atar

J.A.Tostevin, A. Gade Phys. Rev. C 90, 057602 (2014)

Latest compilation including
exotic nuclei from (e,e'p), protonand neutron removal reactions

One-nucleon knockout reactionsat intermediate energies

Reduction factor relative to a certain
Shell Model:
Rs = σexp / σSM
correlations are partially included!

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.20173

Ab-initio Theory: Weak Dependence
SCGF with chiral NNLO-sat interactions
weak ΔS dependence from 0.6 to 0.9

C. Barbieri, private communication (July/2016).

Coupled-cluster calculations with N2LO NN
weak ΔS dependence with further decreaseat the dripline due to coupling to continuum

Jensen et al. Phys. Rev. Lett. 107, 032501 (2011)

Disagreement with knockout experiments atintermediate energies analyzed with eikonal theory!
Leyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.20174Knockout Reactions at Intermediate Energies
on light nuclear targets (e.g. Be, C)
Intermediate beam energy ~ 100MeV/u
nucleon from projectile scatteredeikonal & sudden approximations
strong absorption → surface localized
A. Gade et al. PNP 60(1):161-224,2008

PA-1 = - Pp/n
residue momentum→ angularmomentum ℓ of removed nucleon

Leyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.20175Knockout Reactions at Intermediate Energies
on light nuclear targets (e.g. Be, C)
Intermediate beam energy ~ 100MeV/u
nucleon from projectile scatteredeikonal & sudden approximations
strong absorption → surface localized
A. Gade et al. PNP 60(1):161-224,2008

Measurements

Deduced quantities

cross section → reduction/spectroscopic factor
Momentum distribution → angular momentum ℓγ-ray spectroscopy → selection of final channel

Leyla Atar

PA-1 = - Pp/n
residue momentum→ angularmomentum ℓ of removed nucleon| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.20176

Complementary Approach: Quasi-free Scattering at High Energies
proton target → quasi-free NN reaction
and more sensitivity to deeply bound states)θ1)θ2

Relativistic energies (0.2-1 GeV/u)

Aumann et al. Phys. Rev. C 88, 064610 (2013)

γ-ray

Leyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, AustriaNucleon removal probability
12C vs p-target @ 500AMeV| 17.01.20177

Complementary Approach: Quasi-free Scattering at High Energies
proton target → quasi-free NN reaction
and more sensitivity to deeply bound states)θ1)θ2

Relativistic energies (0.2-1 GeV/u)→ sudden approximation:
fast reaction (10-23 s) and spectator core
→ weaker absorption in nucleus→ free NN cross section is min (~300 MeV)

γ-ray

→ momentum of residue corresponds tomomentum of knocked nucleon

projectile and target nucleon scatteredPA-1 = - Pp/nresidue momentum→ angularmomentum ℓ of removed nucleon

cross section →R/C2S
momentum →ℓγ-ray →final channel
Leyla AtarAumann et al. Phys. Rev. C 88, 064610 (2013)

eikonal approximation| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria

Nucleon removal probability
12
C vs p-target @ 500AMeV| 17.01.2017

8

Oxygen Isotopic Chain
Changing of single-particle strength with proton-neutron asymmetry
Oxygen isotopic chain offers a large variation in isospin
Systematic study of Oxygen isotopes via quasi-free (p,pn) & (p,2p) reactions

neutron knockout

proton knockout

O

14N

1313N

11Leyla Atar12O

17N

16O

16N15O

15

N

14O

18

N

17O

19O

20

N

18N

1923

N

2222

N

2121

N

20

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria

OO

O| 17.01.2017

O

24

O

N
9

GSI Accelerator Facility
Fragmentation of primary 490 AMeV 40Ar beam on 9Be target (3*1010 ion/spill)
Selection of radioactive beam at Fragment Separator (FRS) by in-flight method
Secondary beam 13-24O delivered to Cave CLeyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.2017

10S393 Experiment at R3B/LAND Setup @ GSI
Neutrons(ΔE,t,x,y,z)(x)(ΔE,x,y)(ΔE,E,t)beam(t)FRS/S8(Bρ,t)
Leyla Atar

(ΔE)

Fragments(ΔE,t,x,y)

162 NaI crystals
gamma-rays → 4π detection
nucleons → 2π detection

A1
∝Bρ
Z
βγ

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.2017

Picture taken from S. Altstadttargets (CH2,C) are located inside theγ-detector CB & surrounded by SSDs

11

Incoming Beam & Outgoing Fragment Identification

16O17O

18

Setting A/Z=2
contains 16-18O

O

Incoming beamidentification
Z=8
Z=7

beam
FRS/S8

Leyla Atar

Energy loss in
SST3 vs TFW
for 16O beam

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201712

Incoming Beam & Outgoing Fragment Identification

16O

17

O18

Setting A/Z=2
contains 16-18OObeam
FRS/S8

Leyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201713

Experimental Results

neutron knockout

proton knockout

O

14

N

13

13

11

N

12

O

17

N

16

O

16

N

15

O

15

N

14

O

18

N

17

O

19

O

20

N

18

N

19

23

N

22

22

N

21

21

N

20

O

O

O

O

N

O

24

Inclusive Cross Section & Transverse Momentum: 16O(p,2p)15N
O

Reaction theory: C. Bertulani, eikonal theory16

π 1p1/2

ν 1p1/2

π 1p3/2

ν 1p3/2

π 1s1/2

ν 1s1/2

σexp [mb]28(1)σtheo(1p1/2)

13

σtheo(1p3/2)

25R0.73(3)Sp/n [MeV]

12/16

Leyla Atar

T. Aumann, C. Bertulani, J. Ryckebusch Phys. Rev. C88, 064610 (2013)

Multiple scattering → Glauber model
Absorption → complex optical potential
Only bound core excited states considered

Reduction factor
R = σexp/σtheo(IPM)

R = 0.65(5)from(e,e'p) @ NIKHEF→ agreement!
L. Lapikas Nucl. Phys.
A553, 297c (1993)| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201715

Inclusive Cross Section & Transverse Momentum: 16O(p,2p)15NO

Reaction theory: C. Bertulani, eikonal theory16

π 1p1/2

ν 1p1/2

π 1p3/2

ν 1p3/2

π 1s1/2

ν 1s1/2

σexp [mb]27(1)σtheo(1p1/2)

13

σtheo(1p3/2)

25

R0.70(3)Sp/n [MeV]

12/16

Leyla AtarT. Aumann, C. Bertulani, J. Ryckebusch Phys. Rev. C88, 064610 (2013)

Multiple scattering → Glauber model
Absorption → complex optical potential
Only bound core excited states considered

Reduction factor
R = σexp/σtheo(IPM)

R = 0.65(5)from(e,e'p) @ NIKHEF→ agreement!
L. Lapikas Nucl. Phys.
A553, 297c (1993)| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria

Inclusive Py distribution for
1p1/2 and 1p3/2 proton knockout| 17.01.201716

Partial Cross Sections and Spectroscopic Factors: 16O(p,2p)15N
Doppler corrected γ-spectrum measured
in coincidence with 16O(p,2p)15N

3/23/20.0 MeV 6.3 MeV 9.9 MeV
1/2-πJb (%)

36(5)

47(4)

17(3)

σexp [mb]

10(2)

13(1)

5(1)

C2 S

1.5(3)

2.1(2)

0.7(1)

Spectroscopic factors deduced from thetheoretical predictions and partial cross sections
obtained from the fit of the γ-spectrum.

C2S (e,e'p)

1.3(1)

2.4(2)

0.1(2)← (e,e'p) @ NIKHEF

Leyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201717

Fission Reactions of Neutron-rich Nuclei via quasi-free(p,2p) ScatteringWhy Fission Barrier Studies of n-rich Nuclei?
Experimentally known
fission barriers

r-process

http://www-nds..iaea.org/RIPL-2

Termination of r-process, which is very sensitive to the fission barrier
Experimentally, fission barriers are known only around the stability line.
→ extrapolating of fission barriers in the theory→ uncertainties in the theoretical parameters→ discrepancies between different approaches
Leyla Atar| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201720

Why Fission Studies via Quasi-free (p,2p)
Transfer reactions: thin d-target and low beam energy → low reaction rate &low excitation states & complex reaction → more backgroundQF (p,2p): thick p-target and high beam energy → high reaction rate &high excitation states & clean reaction → less backgroundpp
ProjectileZ

Projectile-likeZ-1pndp

These studies allow us to enhance our knowledge inFission products- isospin dependence of fission barriers- fragment mass distribution (asymmetric vs symmetric)- recycling of the r-process
Leyla Atar

| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201721

Why Fission Studies via Quasi-free (p,2p)
Transfer reactions: thin d-target and low beam energy → low reaction rate &low excitation states & complex reaction → more backgroundQF (p,2p): thick p-target and high beam energy → high reaction rate &high excitation states & clean reaction → less backgroundpp
ProjectileZ

Projectile-like
Z-1

pndp

These studies allow us to enhance our knowledge inFission products- isospin dependence of fission barriers- fragment mass distribution (asymmetric vs symmetric)- recycling of the r-process
Leyla Atar| AG Aumann, TU Darmstadt, Germany | Hirschegg 2017, Kleinwalsertal, Austria| 17.01.201721

Summary
Quasi-free knockout reactions in inverse kinematics provide a direct tool toobtain spectroscopic information.
Inclusive cross sections were measured for the projectiles 13-18O and 21-23O.
The reduction factor obtained from 16O(p,2p)15N reaction is in agreement withthe results from the (e,e'p) reaction at NIKHEF facility.
A weak or no dependence of single-particle strength on the isospin asymmetry
has been observed.
It is necessary to understand the reaction mechanism of knockout for deeply
bound states at intermediate energies.
Fission barrier height of n-rich nuclei plays an important role in theunderstanding of the r-process.
The future R3B/FAIR setup offers an experimental accessibility to the rprocess region.

Thanksfor your attention

TheCollaboration

Aksouh, Farouk; Al-Khalili, Jim; Algora, Alejandro; Alkhasov, Georgij; Altstadt, Sebastian; Alvarez, Hector; Atar, Leyla; Audouin, Laurent; Aumann, Thomas; Pellereau, Eric;
Martin, Julie-Fiona; Gorbinet, Thomas; Seddon, Dave; Kogimtzis, Mos; Avdeichikov, Vladimir; Barton, Charles; Bayram, Murat; Belier, Gilbert; Bemmerer, Daniel; MichaelBendel; Benlliure, Jose; Bertulani, Carlos; Bhattacharya, Sudeb; Bhattacharya, Chandana; Le Bleis, Tudi; Boilley, David; Boretzky, Konstanze; Borge, Maria Jose; Botvina,Alexander; Boudard, Alain; Boutoux, Guillaume; Boehmer, Michael; Caesar, Christoph; Calvino, Francisco; Casarejos, Enrique; Catford, Wilton; Cederkall, Joakim; Cederwall,Bo; Chapman, Robert; Alexandre Charpy; Chartier, Marielle; Chatillon, Audrey; Chen, Ruofu; Christophe, Mayri; Chulkov, Leonid; Coleman-Smith, Patrick; Cortina, Dolores;
Crespo, Raquel; Csatlos, Margit; Cullen, David; Czech, Bronislaw; Danilin, Boris; Davinson, Tom; Paloma Diaz; Dillmann, Iris; Fernandez Dominguez, Beatriz; Ducret, JeanEric; Duran, Ignacio; Egelhof, Peter; Elekes, Zoltan; Emling, Hans; Enders, Joachim; Eremin, Vladimir; Ershov, Sergey N.; Ershova, Olga; Eronen, Simo; Estrade, Alfredo;
Faestermann, Thomas; Fedorov, Dmitri; Feldmeier, Hans; Le Fevre, Arnaud; Fomichev, Andrey; Forssen, Christian; Freeman, Sean; Freer, Martin; Friese, Juergen; Fynbo,Hans; Gacsi, Zoltan; Garrido, Eduardo; Gasparic, Igor; Gastineau, Bernard; Geissel, Hans; Gelletly, William; Genolini, B.; Gerl, Juergen; Gernhaeuser, Roman; Golovkov,Mikhail; Golubev, Pavel; Grant, Alan; Grigorenko, Leonid; Grosse, Eckart; Gulyas, Janos; Goebel, Kathrin; Gorska, Magdalena; Haas, Oliver Sebastian; Haiduc, Maria;
Hasegan, Dumitru; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Ana Henriques; Hoffmann, Jan; Holl, Matthias; Hunyadi, Matyas; Ignatov, Alexander; Ignatyuk,Anatoly V.; Ilie, Cherciu Madalin; Isaak, Johann; Isaksson, Lennart; Jakobsson, Bo; Jensen, Aksel; Johansen, Jacob; Johansson, Hakan; Johnson, Ron; Jonson, Bjoern;
Junghans, Arnd; Jurado, Beatriz; Jaehrling, Simon; Kailas, S.; Kalantar, Nasser; Kalliopuska, Juha; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Kezzar, Khalid; Khanzadeev,Alexei; Kissel, Robert; Kisselev, Oleg; Klimkiewicz, Adam; Kmiecik, Maria; Koerper, Daniel; Kojouharov, Ivan; Korsheninnikov, Alexei; Korten, Wolfram; Krasznahorkay, Attila;
Kratz, Jens Volker; Kresan, Dima; Anatoli Krivchitch; Kroell, Thorsten; Krupko, Sergey; Kruecken, Reiner; Kulessa, Reinhard; Kurz, Nikolaus; Kuzmin, Eugenii; Labiche, Marc;
Langanke, Karl-Heinz; Langer, Christoph; Lapoux, Valerie; Larsson, Kristian; Laurent, Benoit; Lazarus, Ian; Le, Xuan Chung; Leifels, Yvonne; Lemmon, Roy; Lenske, Horst;
Lepine-Szily, Alinka; Leray, Sylvie; Letts, Simon; Li, Songlin; Liang, Xiaoying; Lindberg, Simon; Lindsay, Scott; Litvinov, Yuri; Lukasik, Jerzy; Loeher, Bastian; Mahata, Kripamay;
Maj, Adam; Marganiec, Justyna; Meister, Mikael; Mittig, Wolfgang; Movsesyan, Alina; Mutterer, Manfred; Muentz, Christian; Nacher, Enrique; Najafi, Ali; Nakamura, Takashi;
Neff, Thomas; Nilsson, Thomas; Nociforo, Chiara; Nolan, Paul; Nolen, Jerry; Nyman, Goran; Obertelli, Alexandre; Obradors, Diego; Ogloblin, Aleksey; Oi, Makito; Palit,Rudrajyoti; Panin, Valerii; Paradela, Carlos; Paschalis, Stefanos; Pawlowski, Piotr; Petri, Marina; Pietralla, Norbert; Pietras, Ben; Pietri, Stephane; Plag, Ralf; Podolyak, Zsolt;
Pollacco, Emanuel; Potlog, Mihai; Datta Pramanik, Ushasi; Prasad, Rajeshwari; Fraile Prieto, Luis Mario; Pucknell, Vic; Galaviz -Redondo, Daniel; Regan, Patrick; Reifarth,Rene; Reinhardt, Tobias; Reiter, Peter; Rejmund, Fanny; Ricciardi, Maria Valentina; Richter, Achim; Rigollet, Catherine; Riisager, Karsten; Rodin, Alexander; Rossi, Dominic;
Roussel-Chomaz, Patricia; Gonzalez Rozas, Yago; Rubio, Berta; Roeder, Marko; Saito, Takehiko; Salsac, Marie-Delphine; Rodriguez Sanchez, Jose Luis; Santosh,Chakraborty; Savajols, Herve; Savran, Deniz; Scheit, Heiko; Schindler, Fabia; Schmidt, Karl-Heinz; Schmitt, Christelle; Schnorrenberger, Linda; Schrieder, Gerhard; Schrock,Philipp; Sharma, Manoj Kumar; Sherrill, Bradley; Shrivastava, Aradhana; Shulgina, Natalia; Sidorchuk, Sergey; Silva, Joel; Simenel, Cedric; Simon, Haik; Simpson, John; Singh,Pushpendra Pal; Sonnabend, Kerstin; Spohr, Klaus; Stanoiu, Mihai; Stevenson, Paul; Strachan, Jon; Streicher, Brano; Stroth, Joachim; Syndikus, Ina; Suemmerer, Klaus;
Taieb, Julien; Tain, Jose L.; Tanihata, Isao; Tashenov, Stanislav; Tassan-Got, Laurent; Tengblad, Olof; Teubig, Pamela; Thies, Ronja; Togano, Yasuhiro; Tostevin, Jeffrey A.;
Trautmann, Wolfgang; Tuboltsev, Yuri; Turrion, Manuela; Typel, Stefan; Udias-Moinelo, Jose; Vaagen, Jan; Velho, Paulo; Verbitskaya, Elena; Veselsky, Martin; Wagner,Andreas; Walus, Wladyslaw; Wamers, Felix; Weick, Helmut; Wimmer, Christine; Winfield, John; Winkler, Martin; Woods, Phil; Xu, Hushan; Yakorev, Dmitry; Zegers, Remco;
Zhang, Yu-Hu; Zhukov, Mikhail; Zieblinski, Miroslaw; Zilges, Andreas;