Ⅵ. ORGANIZATION AND ACTIVITIES OF RNC

RIKEN Accel. Prog. Rep. 56 (2023)

Subnuclear System Research Division
RIKEN BNL Research Center
Theory Group
1. Abstract

The eﬀorts of the RBRC theory group are concentrated on the major topics of interest in High Energy Nuclear Physics, inparticular, the physics explored by the RHIC experiment at Brookhaven National Laboratory (BNL). This includes: understandingof the Quark-Gluon Plasma (QGP); the nature of dense quark matter; the initial state in high energy collisions, the Color Glass
Condensate and its evolution to QGP through a Glasma; QCD spin physics; physics relevant to the future Electron-Ion Collider at
BNL.

2. Major Research Subjects(1) Heavy Ion Collisions, QCD phase diagram(2) Perturbative Quantum Chromo-Dynamics (QCD)(3) Nucleon structure, mass and spin

3. Summary of Research Activity(1) Chiral and trace anomalies in Deeply Virtual Compton Scattering
Y. Hatta, S. Bhattacharya and a collaborator discovered novel ‘anomaly poles’ in QCD Compton scattering. These are poles 1/t
in momentum transfer t in oﬀ-forward scattering and are manifestations of the underlying QCD chiral and trace anomalies. This has
signiﬁcant implications for the future tomographic study of the nucleon through the generalized parton distributions (GPDs).
(2) Gravitational form factors in holographic QCD
Y. Hatta and collaborators computed one of the gravitational form factors, the so-called D-term, in holographic QCD using the
Sakai-Sugimoto model. This is the ﬁrst computation of the gravitational form factors in top-down holographic QCD. They foundthat the D-term exhibits the phenomenon of glueball dominance, similar to the vector meson dominance of the electromagnetic form
factors.
(3) Small-x behavior of the GPD Eg(x)Y. Hatta and a collaborator derived, for the ﬁrst time, the small-x evolution equation for the gluon GPD Eg(x). It has been shown
that, despite its association with nucleon helicity-ﬂip processes, Eg(x) grows rapidly with decreasing x in exactly the same way as the
BFKL Pomeron.
(4) Lee-Yang edge singularity
V. Skokov and collaborators employ the functional renormalization group approach at next-to-leading order of the derivative
expansion to reﬁne their earlier ﬁndings for the universal location of the Yang-Lee edge singularity in classic O(N) universality
classes. To this date, it is the most precise determination of the Yang-Lee edge singularity.
(5) CGC for ultraperipheral nuclear collisions
V. Skokov and collaborators provided the ﬁrst calculation of two-gluon production at mid-rapidity in ultra-peripheral collisions in
the Color Glass Condensate framework. To estimate systematic uncertainty associated with poor understanding of the wave functionof the nearly real photon, they consider two diametrically diﬀerent models: the dilute quark-antiquark dipole approximation and avector meson, in which color charge density is approximated by McLerran-Venugopalan model.
(6) Simulating the tiniest ﬂuids in 3 + 1 dimensions
Employing a dynamical initial state model coupled to (3 + 1)D viscous relativistic hydrodynamics, C. Shen and collaborators
explored the rapidity dependence of anisotropic ﬂow in the Relativistic Heavy-Ion Collider (RHIC) small system scan at 200 GeV
center of mass energy [6]. They demonstrate that approximately 50% of the pT -diﬀerential triangular ﬂow diﬀerence between themeasurements by the STAR and PHENIX Collaborations can be explained by the use of reference ﬂow vectors from diﬀerent rapidity
regions. This emphasizes the importance of longitudinal ﬂow decorrelation for anisotropic ﬂow measurements in asymmetric nuclear
collisions and the need for (3 + 1)D simulations.
(7) Multi-scale imaging of nuclei geometry at high energy
C. Shen and collaborators showed that the failure to describe the v2 ratio in central UU and AuAu collisions at RHIC was due toinappropriate treatments of well-deformed nuclei in modeling the initial conditions of the QGP [8]. With rigorous input from Skyrme
density functional calculations, they show that correcting nuclear deformations in hydrodynamic simulations restores agreement with
BNL RHIC data. This brings consistency to the results of nuclear experiments across energy scales and demonstrates the impact of
the hexadecapole deformation of Uranium nucleus on high-energy collisions.

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Ⅵ. ORGANIZATION AND ACTIVITIES OF RNC

RIKEN Accel. Prog. Rep. 56 (2023)(8) Renormalization of jet quenching parameter
Y. Mehtar-Tani and collaborators demonstrated that the leading quantum corrections to parton energy loss can be resummed andincorporated through a renormalization of the jet quenching parameter, while still preserving the classical tree-level framework. The
renormalized jet quenching now depends on the length of the medium, owing to non-local quantum eﬀects, resulting in a weakly
non-Markovian dynamics. Based on this theory result, they developed a systematic approach with signiﬁcant implications for jet
quenching phenomenology.

Members
Group Leader
Yoshitaka HATTARBRC Researchers
Yacine MEHTAR-TANI
Chun SHEN

Vladimir SKOKOV
Bhattacharya SHOHINI

List of Publications & Presentations
Publications[Original Papers]
Y. Hatta, B. Xiao, and F. Yuan, “Semi-inclusive diﬀractive deep inelastic scattering at small-x,” Phys. Rev. D 106, 094015 (2022).
M. Fujita, Y. Hatta, S. Sugimoto, and T. Ueda, “Nucleon D-term in holographic quantum chromodynamics,” Prog. Theor. Exp. Phys,
2022, 093B06 (2022).
Y. Hatta and J. Zhou, “Small-x evolution of the gluon GPD Eg,” Phys. Rev. Lett. 129, 25 (2022).
S. Bhattacharya, Y. Hatta, and W. Vogelsang, “Chiral and trace anomalies in deeply virtual Compton scattering,” Phys. Rev. D 107, 014026(2023).
A. Kumar et al. [JETSCAPE], “Inclusive jet and hadron suppression in a multistage approach,” Phys. Rev. C 107, 034911 (2023).
K. J. Sun, R. Wang, C. M. Ko, Y. G. Ma, and C. Shen, “Unveiling the dynamics of nucleosynthesis in relativistic heavy-ion collisions,”
arXiv:2207.12532.
W. Fan et al. [JETSCAPE], “Multiscale evolution of charmed particles in a nuclear medium,” Phys. Rev. C 107, 054901 (2023).
H. Alalawi, J. Boyd, C. Shen, and M. Strickland, “Impact of ﬂuctuating initial conditions on bottomonium suppression in 5.02 TeV
heavy-ion collisions,” Phys. Rev. C 107, L031901 (2023).
L. Du, C. Shen, S. Jeon, and C. Gale, “Probing initial baryon stopping and equation of state with rapidity-dependent directed ﬂow ofidentiﬁed particles,” arXiv:2211.16408.
W. Zhao, S. Ryu, C. Shen, and B. Schenke, “3D structure of anisotropic ﬂow in small collision systems at energies available at the BNL
Relativistic Heavy Ion Collider,” Phys. Rev. C 107, 014904 (2023).
Y. Tachibana et al. [JETSCAPE], “Hard jet substructure in a multi-stage approach,” arXiv:2301.02485.
W. Ryssens, G. Giacalone, B. Schenke, and C. Shen, “Evidence of hexadecapole deformation in uranium-238 at the relativistic heavy ion
collider,” accepted by Phys. Rev. Lett, arXiv:2302.13617.
H. Mäntysaari, B. Schenke, C. Shen, and W. Zhao, “Multi-scale imaging of nuclear deformation at the electron ion collider,”arXiv:2303.04866.
T. Schaefer and V. Skokov, “Dynamics of non-Gaussian ﬂuctuations in model A,” Phys. Rev. D 106, 014006 (2022).
H. Duan, A. Kovner, and V. V. Skokov, “CGC for ultra-peripheral Pb + Pb collisions at the Large Hadron Collider: a more realistic
calculation,” J. High Energy Phys. 12, 077 (2022).
G. Johnson, F. Rennecke, and V. V. Skokov, “Universal location of Yang-Lee edge singularity in classic O(N) universality classes,”arXiv:2211.00710.
H. Duan, A. Kovner, and V. V. Skokov, “Classical entanglement and entropy,” arXiv:2301.05735.
P. Caucal and Y. Mehtar-Tani, “Universality aspects of quantum corrections to transverse momentum broadening in QCD media,” J. HighEnergy Phys. 09, 023 (2022).
P. Caucal and Y. Mehtar-Tani, “Transverse momentum broadening from NLL BFKL to all orders in pQCD,” arXiv:2209.08900.
Y. Mehtar-Tani, S. Schlichting, and I. Soudi, “Jet thermalization in QCD kinetic theory,” arXiv:2209.10569.

[Proceedings]
Y. Hatta, “Nucleon EDM from polarized DIS,” JPS Conf. Proc. 37, 020601 (2022).
S. Benic, Y. Hatta, A. Kaushik, and H. Li, “A novel contribution to single spin asymmetries in SIDIS at two loops,” JPS Conf. Proc. 37,
020203 (2022).
S. Bhattacharya, K. Cichy, M. Constantinou, J. Dodson, X. Gao, A. Metz, S. Mukherjee, A. Scapellato, F. Steﬀens, and Y. Zhao, “GPDsin asymmetric frames,” PoS Lattice 2022, 095 (2023).
H. Mäntysaari, B. Schenke, C. Shen, and W. Zhao, “Bayesian inference of the ﬂuctuating proton shape in DIS and hadronic collisions,”
Acta Phys. Polon. Supp. 16, 33 (2023).

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V. Vovchenko, V. Koch, and C. Shen, “Proton number cumulants and correlation functions from hydrodynamics and the QCD phase
diagram,” Acta Phys. Polon. Supp. 16, 83 (2023).
C. Shen, W. Zhao, and B. Schenke, “Collectivity in ultra-peripheral heavy-ion collisions,” EPJ Web Conf. 276, 01002 (2023).
Y. Tachibana, C. Shen et al. [JETSCAPE], “Comprehensive study of multi-scale jet-medium interaction,” arXiv:2212.12188.

Presentations[International Conferences/Workshops]
Y. Hatta (invited), “EIC science: ep reactions,” Town hall meeting on hot & cold QCD, USA (MIT), September 20–22, 2022.
Y. Hatta (invited), “Nucleon D-term in the Sakai-Sugimoto model,” INT Workshop on Origin of the Visible Universe: Unraveling theProton Mass, USA (University of Washington), June 13–17, 2022.
Y. Hatta (invited), “Experimental observables to access GTMDs,” Towards improved hadron femtography with hard exclusive reactions,
USA (Virginia Tech University), July 18–22, 2022.
Y. Hatta (invited), “Nucleon EDM and polarized DIS,” QCD evolution, University of Virginia, May 9–13, 2022.
Y. Hatta (invited), “Azimuthal angular correlation of jets from soft gluon radiation,” RBRC workshop on predictions for sPHENIX, USA(BNL), July 20–22, 2022.
S. Bhattacharya (invited), “Hunting for gluon orbital angular momentum at the EIC,” XXIX Cracow Epiphany Conference on Physics atthe EIC and Future Facilities, Cracow, Poland, January 18, 2023.
S. Bhattacharya (invited), “Chiral and trace anomalies in DVCS,” CFNS Meetings, USA (Stony Brook University), March 10, 2023.
C. Shen (selected contributed talk), “Collectivity and baryon junctions in ultra-peripheral heavy-ion collisions,” the 20th International
Conference on Strangeness in Quark Matter, June 14, 2022.
C. Shen (invited), “Going beyond ﬂow: Did we hit the precision wall?,” First CMS Heavy-Ion Workshop, August 8, 2022.
C. Shen (invited), “Multi-messenger heavy-ion physics with JETSCAPE,” 13th International workshop on Multiple Partonic Interactionsat LHC, November 15, 2022.
C. Shen (invited), “3D modeling of the RHIC isobar collisions,” Intersection of Nuclear Structure and High-energy Nuclear Collisions,February 17, 2023.
C. Shen (invited), “Illuminating early-stage dynamics of heavy-ion collisions through photons at RHIC BES energies,” 11th International
Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collision, March 29, 2023.
Y. Mehtar-Tani (invited), “Quantum induced anomalous diﬀusion in QCD matter,” Jet Quenching In The Quark-Gluon Plasma workshop,
ECT*, Trento, June 13–17, 2022.
Y. Mehtar-Tani (invited), “Transverse momentum broadening from NLL BFKL to all orders in pQCD,” Resummation Evolution Factorization, October 31–November 4, 2022.
Y. Mehtar-Tani (invited), “Jet energy loss and heavy ﬂavor, Heavy Flavors from small to large systems,” Institut Pascal Program, Orsay,
France (Paris-Saclay University), October 3–21, 2022.
Y. Mehtar-Tani (invited), “Transverse momentum broadening from NLL BFKL to all orders in pQCD,” 13th international workshop on
Multiple Partonic Interactions at the LHC, Madrid, Spain, November 14–18, 2022.

[Domestic Conference/Workshop]
Y. Hatta (invited), “Nucleon graivitational form factors in holographic QCD,” Third International Workshop on the Extension Project for
the J-PARC, Hadron experimental facility, Japan (J-PARC), March 14–16, 2023.

[Seminars]
Y. Hatta, “QCD spin physics at the EIC,” Heavy-ion tea seminar, USA (Lawrence Berkeley National Laboratory), October 14, 2022.
Y. Hatta, “Chiral and trace anomalies in DVCS,” Stony Brook, USA, November 2, 2022.
Y. Hatta, “Azimuthal angular asymmetry of soft gluons in jet production, USA (Yale University), April 28, 2022.
Y. Hatta, “Near-threshold quarkonium production and the nucleon gravitational form factors,” CFNS seminar, USA (Stony Brook University), August 25, 2022.
S. Bhattacharya, “Primary observables to access orbital angular momentum of partons,” Nuclear Physics Seminar, USA (University of
Illinois Urbana-Champaign), February 13, 2023.
S. Bhattacharya, “Computing PDFs and GPDs in Lattice QCD: Recent Progress,” Center for Nuclear Theory seminar, USA (Stony Brook
University), February 22, 2023.
C. Shen, “Longitudinal dynamics and particle production in relativistic nuclear collisions,” RBRC seminar, July 7, 2022.
C. Shen, “Flowing through the nuclear phase diagram at the highest temperatures and densities,” Physics colloquium at Wayne State
University, October 6, 2022.
C. Shen, “3D modeling of the collective behaviors in relativistic heavy-ion collision,” Nuclear Seminar at HENPIC-EVO, December 22,
2022.
C. Shen, “3D modeling of the collective behaviors in relativistic heavy-ion collisions,” Nuclear Seminar at Iowa State University, February
23, 2023.
Y. Mehtar-Tani, “The hottest matter under the microscope: probing the quark gluon plasma at colliders,” BNL lecture, Upton (BNL),
December 14, 2022.
Y. Mehtar-Tani, “Quantum induced anomalous diﬀusion in QCD matter,” Teilchentee seminar at ITP, Heidelberg, Germanuy (Heidelberg- 359 -

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University), June 2, 2022.
Y. Mehtar-Tani, “3D-structure of the proton: from partons to strong ﬁelds,” UCLA Nuclear Physics Group, Los Angeles, CA (UCLA),
September 15, 2022.

Press Release
S. Bhattacharya, R. Boussarie, and Y. Hatta, “Theorists propose a novel way to measure gluons’ orbital motion,” DOE highlights, November 10, 2022.

Awards
C. Shen, 2023 Outstanding Junior Faculty Award, Wayne State Academy of Scholars, https://academy.wayne.edu/junior-award .
V. Skokov, LeRoy and Elva Martin Award for Teaching Excellence (NCSU).

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