Nuclear Theory·nucl-th

Wednesday·December 3, 2025

8 papers—6 primary·2 cross-listed

01
[Submitted on 1 Dec 2025]
Modifications in clusterization procedures for heavy-ion collisions: minimum spanning tree, simulated annealing, coalescence
Viktar Kireyeu🇷🇺
A new open-source cluster finding library ''Common Clusterization Library'' (CCL) is proposed to describe the clusters production when applied to the transport codes. The new library was applied to the Parton-Hadron-Quantum-Molecular Dynamics approach to be comparable with the established and well known MST and SACA implementations on the exactly same set of the events. The presented procedures were tested with rapidity density distributions and complex observables like $⟨ M_{im f} ⟩$ and $⟨ Z_{max} ⟩$ vs $Z_{b o u n d} 2$ at the energies of ALADiN and NA49 experiments. An improvement to the simulated annealing chain is proposed to reduce the computational time. The new stable clusters tracking algorithm for the ''lost'' cluster recovering is presented. The results of the ''box-like'' coalescence procedure and a mixed method which incorporates the coalescence algorithm steps and the negative binding energy criteria are presented. The difference between the Helium-3 found by the MST-based cluster finding procedure and the coalescence algorithm applied on the exactly same set of events and baryons is shown for the first time.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2512.02084 [pdf]
Comput.Phys.Commun.(2026)·1 citation
02
[Submitted on 1 Dec 2025]
Uncertainty Principle and Angular Momentum Generation in Microscopic Fission Models
G. Scamps🇫🇷 · A. Guilleux🇫🇷 · D. Regnier🇫🇷 · A. Bernard🇫🇷
The generation of angular momentum (intrinsic spin) in fission fragments has recently attracted renewed attention. While several microscopic approaches reproduce the spin distribution qualitatively using projection techniques, the physical origin of the fragments' angular momentum in density functional theory remains unclear. In this work, we investigate the mechanisms responsible for the spin distribution of fission fragments within a microscopic TDDFT framework. We compare spin distributions obtained from projection operators with those predicted by a simple expression derived from the uncertainty relation between angle and angular momentum, where angular fluctuations are estimated using a Monte Carlo sampling of nucleon positions. We find that a large portion of the spin distribution obtained from projection methods can be explained by the uncertainty principle. Our results thus show that, within microscopic approaches, the spin of fission fragments originates primarily from quantum uncertainty associated with their orientation angle with respect to the fission axis, mainly due to quadrupole deformation and, to a lesser extent, octupole deformation.
Comments:
10 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
arXiv:
2512.02207 [pdf]
2 citations
03
[Submitted on 2 Dec 2025]
Neutron-deuteron scattering revisited with the EKM chiral nuclear force and the WPCD method
Qing-Yu Zhai🇨🇳 · Dan-Yang Pang🇨🇳 · Wen-Di Chen🇨🇳 · O. A. Rubtsova🇷🇺 · Rui-Rui Xu🇨🇳 · Jun-Xu Lu🇨🇳 · Haozhao Liang🇯🇵 · Li-Sheng Geng🇨🇳
We revisit the neutron-deuteron scattering using the Wave-Packet Continuum Discretization (WPCD) method with the EKM chiral nuclear force at various chiral orders. We rederive the permutation operator and solve the Faddeev-AGS equations directly, without rewriting the initial Faddeev kernel $t G_{0}$ and introducing pseudo-states, thereby rendering the approach easily extendable to a relativistic framework. We find that up to the next-to-next-to-next-to-leading order (N $^{3}$ LO), although one can well describe the differential cross sections, one cannot resolve the long-standing $A_{y}$ puzzle, consistent with previous studies. The fact that the N $^{3}$ LO chiral forces can well describe the $N N$ phase shifts and the results obtained with the EKM and Idaho N $^{3}$ LO chiral forces agree with each other underscores the need for further investigations to resolve the $A_{y}$ puzzle, e.g., considering three-body forces or relativistic effects.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2512.02475 [pdf]
PRC(2026)·1 citation
04
[Submitted on 2 Dec 2025]
Excitation function of femtoscopic Lévy source parameters of pion pairs in EPOS4
Yan Huang🇭🇺 · Matyas Molnar🇭🇺 · Daniel Kincses🇭🇺 · Mate Csanad🇭🇺
Three-dimensional (3D) femtoscopic source parameters of pions provide a sensitive probe of the space-time structure of particle-emitting sources in high-energy heavy-ion collisions. Compared to one-dimensional measurements, three-dimensional femtoscopy not only provides a valuable cross-check but also offers a more complete characterization of the source geometry and its dynamical evolution. Particularly, differences between the out and side directions are sensitive to signals of a strong first-order phase transition, while the collision-energy dependence of Lévy radii may reveal non-monotonic features related to the equation of state. In this work, we systematically investigate the transverse mass (mT) and collision-energy (sqrt(sNN)) dependence of the three-dimensional femtoscopic parameters of pion pairs with Lévy-type sources in the STAR Beam Energy Scan (BES) range from sqrt(sNN) = 7.7 to 200 GeV using the EPOS4 model. The analyzed parameters include the Lévy index alpha, the correlation strength lambda, and the three-dimensional radii Rout, Rside and Rlong, corresponding to the outward, sideward, and longitudinal (beam) directions. Derived quantities such as the out-side squared radius difference and the out/side ratio are also investigated. The results show that the extracted radii Rside and Rlong decrease with increasing transverse mass and increase gradually with collision energy, while Rout shows little energy dependence. The Lévy index alpha exhibits only a mild dependence on mT and collision energy, whereas the correlation strength lambda shows a clear mT dependence and generally decreases with increasing collision energy. A comparison with EPOS3 results indicates general agreement within approximately 2sigma, with the notable exception of Rside, which is systematically smaller in EPOS4.
Comments:
8 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2512.02560 [pdf]
PLB(2026)·5 citations
05
[Submitted on 2 Dec 2025]
Thermoelectric coefficients of two-flavor quark matter from the Kubo formalism
Harutyun Gabuzyan🇦🇲 · Arus Harutyunyan🇦🇲 · Armen Sedrakian🇩🇪
The hot quark matter created in heavy-ion collision experiments can exhibit strong temperature and chemical-potential gradients, which in turn can generate electric fields through thermoelectric effects. In this work, we investigate two relevant thermoelectric coefficients -- the thermopower (Seebeck coefficient) and the Thomson coefficient -- of two-flavor quark matter using the Kubo formalism and the Nambu--Jona-Lasinio model as an effective description of dense, finite-temperature QCD. The required two-point equilibrium correlation functions are evaluated using the Matsubara formalism of thermal field theory, applying a 1/Nc expansion to the relevant multi-loop Feynman diagrams. We employ previously derived quark spectral functions obtained from one--meson-exchange diagrams above the Mott transition temperature. Our numerical results show that both thermoelectric coefficients increase approximately linearly with temperature and decrease with increasing chemical potential. We also estimate the magnitude of the electric fields that can be generated in heavy-ion collisions by thermal gradients via the Seebeck effect.
Comments:
17 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2512.02602 [pdf]
PRD(2026)·1 citation
06
[Submitted on 2 Dec 2025]
Experimental constraints on $γ$ -ray strength function of $^{72}$ Ga from $^{72} Ga (n, γ)^{72} Ga$ capture data and reevaluation of Maxwellian-averaged cross sections of $^{71}$ Ga
Sajid Ali · Rajkumar Santra · Gautam Gangopahyay
The $γ$ -ray strength function of medium-mass neutron rich nuclei $^{72}$ Ga has been extracted from the statistical Hauser-Feshbach analysis of the available capture data of $^{71} Ga (n, γ)^{72} Ga$ over the 0.01 - 3 MeV energy range with the required nuclear level density (NLD) of the $^{72}$ Ga constraint from the work of R. Santra et al.,[\href{https://doi.org/10.1103/PhysRevC.107.064611}{Physical Review C 107, 064611 (2023)}]. The Gogny D1M model for the E1 and M1 strength functions, including low-energy upbends of $^{72}$ Ga nuclei, is experimentally constrained in the present work. Subsequently, the Maxwellian-averaged cross section(MACS) of $^{71} Ga$ has been reevaluated based on the present $γ$ -ray strength function. It is found that the present MACS value at $kT = 30$ keV is 115.35 $_{- 10.44}^{+ 11.92}$ mb, which is consistent with previous work.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2512.02736 [pdf]
0 citations
07
[Submitted on 2 Dec 2025] (cross-list from hep-ph)
Non-diagonal DVCS with spinless hadron-to-two-hadron transition $γ^{*} π \to γ π π$
Sangyeong Son
We present the formalism of hadron-to-two-hadron transition generalized parton distributions (GPDs) for spinless hadron case. Definitions of the twist-2 unpolarized and polarized $π \to π π$ transition GPDs are introduced with a particular choice of kinematic variables that characterize the produced two-pion system. In the vicinity of $ρ (770)$ , we work out the two-pion decay angular distributions of the $e^{-} π \to e^{-} γ π π$ cross section, incorporating both the Bethe-Heitler and deeply virtual Compton scattering processes. Each cross section exhibits a distinctive angular distribution, which is sensitive to the polarization states of the produced $ρ (770)$ resonance. In addition, we construct the double partial-wave expansion of $π \to π π$ transition GPDs in the two-pion decay angles as a generalization of GPDs for transition from a pion to a spin- $ℓ$ resonance state. With the help of the Omnès representation, we constrain the $π \to π π$ transition GPDs in terms of the low energy $π π$ scattering phase shift and build a phenomenological model for these GPDs.
Comments:
7 pages, 3 figures, Contribution to The 21st International Conference on Hadron Spectroscopy and Structure (HADRON2025)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2512.02407 [pdf]
PoS(2026)·0 citations
08
[Submitted on 2 Dec 2025] (cross-list from nucl-ex)
Evidence of Spin-Interference Effects in Exclusive $J / ψ \to e^{+} e^{-}$ Photoproduction in Ultraperipheral Heavy-Ion Collisions
The STAR Collaboration
We report the first evidence of spin interference in exclusive $J / ψ \to e^{+} e^{-}$ photoproduction in ultraperipheral heavy-ion collisions at STAR at $s_{N N} = 200$ ~GeV. In Au+Au collisions, a negative $cos (2 ϕ)$ modulation is found for $p_{T} < 120$ ~MeV/ $c$ with a significance of $3.2 σ$ , while the isobar data (Ru+Ru, Zr+Zr) show a consistent negative modulation with a significance of $1.9 σ$ , opposite in sign to that in $ρ^{0} \to π^{+} π^{-}$ photoproduction. This establishes for the first time that the interference sign is controlled by the spin structure of the final-state daughters, resolving the ambiguity present in the all-boson $ρ^{0}$ channel. The compact $J / ψ$ probes gluon distributions at perturbative scales, resulting in a weaker modulation and providing stringent constraints on Color Glass Condensate calculations. These findings demonstrate that spin-dependent interference in heavy vector mesons provides a new, experimentally accessible handle on gluon structure beyond traditional cross-section measurements.
Comments:
Accepted for publication in Phys. Rev. Lett
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2512.02865 [pdf]
PRL(2026)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE