Nuclear Theory·nucl-th

Wednesday·February 4, 2026

9 papers—4 primary·5 cross-listed

01
[Submitted on 2 Feb 2026]
Anisotropic time evolution of sound modes in Bjorken expanding holographic plasma
Casey Cartwright🇳🇱 · Ruchi Chudasama🇺🇸 · Sergei Gleyzer🇺🇸 · Durdana Ilyas🇺🇸 · Matthias Kaminski🇺🇸 · Marco Knipfer🇺🇸 · Jun Zhang🇺🇸
The speed of sound is a key parameter for characterizing equilibrium states. However, sound waves change their properties when propagating through rapidly evolving anisotropic media, such as the quark-gluon plasma created in heavy-ion collisions. This paper uses $N = 4$ Super-Yang-Mills theory to numerically study the time evolution of the speed and attenuation of sound modes along with the relaxation time in a plasma undergoing Bjorken expansion from various initial states in a quasi-static approximation. The longitudinal Bjorken expansion breaks the isotropy, resulting in two distinct sound speeds that range from just below the conformal value to the speed of light. An anisotropic hydrodynamic description is constructed and its applicability is discussed. Implications for the analysis of heavy ion data are considered.
Comments:
16 pages, 13 figures, 6 appendices
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
arXiv:
2602.02687 [pdf]
1 citation
02
[Submitted on 2 Feb 2026]
Corrections to the Smoothness and On-Shell Approximations in Femtoscopy and Coalescence
Isaac G. Smith🇮🇱 · Kfir Blum🇮🇱
Relativistic heavy-ion collisions produce femtometer-scale sources whose space-time structure can be constrained using two-particle femtoscopic correlations. Standard implementations rely on the smoothness and on-shell approximations, which effectively remove the relative momentum dependence of the particle emission function. We explore the validity of these approximations by deriving model-independent expansions that quantify the leading corrections for femtoscopy and coalescence with arbitrary sources and final-state interactions. The resulting first- and second-order correction terms can be evaluated with essentially the same numerical complexity as the usual Koonin-Pratt expressions; for angle-averaged correlations the first-order contributions vanish by symmetry. We illustrate the framework with explicit calculations in a blast-wave source model; for blast-wave parameter sets representative of pp and PbPb fits at LHC energies, the corrections are at or below the percent level for pp correlations and deuteron coalescence. These corrections are potentially subdominant compared to other effects, for example, corrections to the equal time approximation.
Comments:
3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex)
arXiv:
2602.02810 [pdf]
PRC(2026)·1 citation
03
[Submitted on 3 Feb 2026]
Neutron skin thickness and its volume and surface contributions in berkelium isotopes
Peng Wang · Zi-Dan Huang · Shuang-Quan Zhang · Ting-Ting Sun
Accurate determination of the neutron skin thickness ( $Δ R_{np}$ ) in finite nuclei is essential for constraining the density dependence of the nuclear symmetry energy. This work presents a systematic investigation of $Δ R_{np}$ for the transuranium berkelium (Bk) isotopes within the framework of the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). The results indicate an overall increase in neutron skin thickness with $N$ , which exhibits antikinks at the shell closures $N = 184, 258$ due to the shell effects. A decomposition of $Δ R_{np}$ into volume and surface terms, based on two-parameter Fermi (2pF) fits to angle-averaged DRHBc densities, demonstrates that the volume term dominates as much as $60%$ -- $70%$ in most nuclei, consistent with the $65%$ found in $^{208}$ Pb, thereby validating the volume-surface decomposition for deformed nuclei and confirming its correlation with the symmetry energy slope $L$ . The surface term prevails only near the proton drip line, where the volume fraction drops below $50%$ due to the reduced neutron-to-proton ratio. Deformation is found to slightly reduce the central radius $R_{c}$ but markedly enhance the surface diffuseness $a$ , leading to a notable increase in $Δ R_{np}$ , primarily driven by the surface term. Furthermore, we extend the decomposition to a directional analysis by extracting 2pF parameters along the symmetry axis ( $θ = 0^{\circ}$ ) and perpendicular to it ( $θ = 9 0^{\circ}$ ). In prolate deformed nuclei, a strong directional dependence is observed: although the nucleus is elongated along the symmetry axis, $Δ R_{np}$ is significantly larger in the perpendicular direction. This anisotropy is weak for oblate nuclei around the shell closures.
Comments:
11 figures, 13 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.03323 [pdf]
PRC(2026)·1 citation
04
[Submitted on 3 Feb 2026]
Exploring Hyperon Skyrme Forces in Multi- $Λ$ Hypernuclei and Neutron Star Matter
X. D. Sun🇨🇳 · S. C. Han🇨🇳 · J. N. Hu🇨🇳 · A. Li🇨🇳
A major source of uncertainty in modeling the strangeness-rich interiors of neutron stars arises from the poorly constrained two-body and three-body interactions among hyperons and nucleons. We perform a comprehensive Bayesian analysis of the $ΛΛ$ and $ΛΛ N$ interaction parameters within the Skyrme Hartree-Fock framework, constrained by both hypernuclei experimental data and astrophysical observations. Our results show that the parameter space of the $ΛΛ$ interaction is tightly constrained by combining nuclear and astrophysical data, while the parameters of the $ΛΛ N$ three-body interaction remain sensitive to astrophysical inputs alone. Specifically, the local, momentum-independent two-body interaction parameter $λ_{0}$ is tightly constrained and predominantly attractive, while the momentum-dependent parameters $λ_{1}$ and $λ_{2}$ contribute repulsive effects at high densities. A key role is played by the $ΛΛ$ potential depth in pure $Λ$ matter, which effectively constrains the two-body $ΛΛ$ interaction and governs the balance between attraction at low densities and repulsion at high densities. The repulsive components of $ΛΛ$ interactions then decrease hyperon fractions and reconcile hyperon-rich equations of state with the observed $\sim 2 M_{⊙}$ neutron stars, increasing the maximum mass by up to 22\%. The inclusion of $ΛΛ N$ three-body forces further stiffens the EOS, raising the maximum mass by up to $\sim 0.1 M_{⊙}$ . Our study represents a promising step toward a complete, experimentally grounded description of dense matter across a wide range of densities and strangeness compositions.
Comments:
18 pages incuding APPENDIX, 9 figures, 7 tables; accepted for publication in MNRAS (2026)
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2602.03388 [pdf]
MNRAS(2026)·14 citations
05
[Submitted on 2 Feb 2026] (cross-list from gr-qc)
Dynamical response of twin stars to perturbations
Shamim Haque🇮🇳 · Luciano Rezzolla🇮🇳 · Ritam Mallick🇮🇳
If a strong first-order phase transition takes place at sufficiently high rest-mass densities in the equation of state (EOS) modelling compact stars, a new branch will appear in the mass-radius sequence of stable equilibria. This branch will be populated by stars comprising a quark-matter core and a hadronic-matter envelope, i.e., hybrid stars, which represent ``twin-star'' solutions to equilibria having the same mass but a fully hadronic EOS. While both branches are stable to linear perturbations, it is unclear which of the twin solutions is the ``favoured'' one, that is, which of the two configurations is expected to be found in nature. We assess this point by performing a large campaign of general-relativistic simulations aimed at assessing the response of compact stars on the two branches to perturbations of various strength. In this way, we find that, independently of whether the stars populate the hadronic or the twin branch, their response is characterised by a critical-perturbation strength such that the star will oscillate on the original branch for subcritical perturbations and migrate to the neighbouring branch for supercritical perturbations while conserving rest-mass. Because the critical values are different for stars with the same rest-mass but sitting on either branch, it is possible to define as favoured the part of the branch that has the largest critical perturbation, thus correcting the common wisdom that stellar models on the twin branch are the favoured ones. Interestingly, we show that the binding energies on the two branches can be used to deduce without simulations which of the stellar configurations is more likely to be found in nature.
Comments:
11 pages, 7 figures, 5 tables, matches the accepted version in Physical Review D
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2602.02654 [pdf]
PRD(2026)·5 citations
06
[Submitted on 2 Feb 2026] (cross-list from hep-ph)
Exploring Thermalization and Multi-Freeze-Out Effects in Pb-Pb collisions Based on Tsallis pT Distributions
Haifa I. Alrebdi🇸🇦 · Muhammad Ajaz🇵🇰 · Murad Badshah🇵🇰 · Mohammad Ayaz Ahmad🇬🇾
This study investigates transverse-momentum (pT) distributions of pi-, pi+, K-, K+, p, pbar, K0s, and Lambda in several centrality classes of Pb-Pb collisions at sqrt(sNN) = 2.76 TeV. The measured spectra are analyzed with the Tsallis non-extensive distribution, from which the effective temperature T, non-extensive parameter q, and the mean transverse momentum mean_pT are extracted for each particle species and centrality interval. To disentangle thermal and collective effects, the mean kinetic freeze-out temperature T0 is obtained from the intercept of the T-versus-mass relation, while the average transverse flow velocity betaT is extracted from the slope of mean_pT versus the mean moving mass for pions, kaons, and protons. The results show that T increases and q decreases with increasing centrality, indicating a hotter and more equilibrated system in central collisions. A clear mass dependence of T supports a multi-freeze-out scenario, with heavier particles decoupling earlier. Both T0 and betaT rise from peripheral to mid-central collisions before saturating toward central events, which may suggest the onset of collective behavior or changes in freeze-out dynamics. These observations provide new insights into the thermal and dynamical properties of the medium created in heavy-ion collisions at the LHC.
Comments:
25 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2602.02679 [pdf]
CPC(2026)·5 citations
07
[Submitted on 2 Feb 2026] (cross-list from hep-ph)
Dark Matter-Induced Nuclear De-Excitation at SBND with Ab Initio Nuclear Theory
Bhaskar Dutta🇷🇴 · Debopam Goswami🇷🇴 · Baishan Hu🇺🇸 · Wei-Chih Huang🇷🇴 · Vishvas Pandey🇺🇸
We explore the sensitivity of the Short-Baseline Near Detector (SBND) experiment to light dark matter using MeV-scale electromagnetic activity. Inelastic scattering of dark matter with argon nuclei can excite nuclear states that subsequently de-excite via the emission of MeV-scale photons, producing localized low-energy "blip" signatures in a liquid argon time projection chamber. We perform state-of-the-art ab initio nuclear calculations, including all relevant argon excited states with energies up to 18 MeV, to provide reliable predictions for these signals. After accounting for relevant backgrounds, we find that SBND can probe previously unexplored regions of parameter space for light dark matter.
Comments:
7 pages, 3 figures, 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2602.02817 [pdf]
3 citations
08
[Submitted on 2 Feb 2026] (cross-list from hep-ph)
Contact interaction treatment of the nucleon Faddeev equation
Xin-Yu Bai🇨🇳 · Ya Lu🇨🇳 · Zhao-Qian Yao🇨🇳 · Craig D. Roberts🇨🇳 · Sebastian M. Schmidt🇨🇳
Working with a symmetry-preserving treatment of a vector*vector contact interaction (SCI), a largely algebraic three-body Faddeev equation treatment of the nucleon bound state problem is introduced and used to deliver results for all nucleon charge and magnetisation distributions and their flavour separation. A strength of the SCI treatment is that it provides for a transparent understanding of this three-body approach to developing predictions for baryon observables. Comparisons of SCI results with predictions obtained in realistic-interaction Faddeev equation studies reveal the sensitivities of a given observable to the pointwise behaviour of the quark-quark interaction and phenomena associated with the emergence of hadron mass.
Comments:
17 pages, 8 figures, 3 tables. Version to appear in Eur. Phys. J. A
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2602.02880 [pdf]
EPJA(2026)·3 citations
09
[Submitted on 3 Feb 2026] (cross-list from hep-ph)
Extraction of the pion-nucleon coupling constant using the effective-range expansion with the left-hand cut
Bo-Yang Liu🇨🇳 · Bing Wu🇨🇳 · Ji-Wei Fu🇨🇳 · Meng-Lin Du🇨🇳 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪
We apply the generalized effective-range expansion of Phys. Rev. Lett. 135, 011903(2025), which incorporates the left-hand cut from one-pion exchange, to low-energy neutron-proton scattering in the $^{1} S_{0}$ and $^{3} S_{1}$ channels. The amplitude zero for the center-of-mass momentum near 0.35 GeV in the $^{1} S_{0}$ channel is naturally accommodated within this framework. We extract the pole position, scattering length, effective range, and the pseudoscalar pion-nucleon coupling constant $g_{π N}^{2} / (4 π)$ at different expansion orders. The low-energy parameters are stable and consistent with established values, while $g_{π N}^{2} / (4 π)$ exhibits larger uncertainties. The extraction of $g_{π N}^{2} / (4 π)$ is data-driven, relying on the analytic constraints from the left-hand cut and phase-shift data within the one-pion-exchange approximation. Despite larger uncertainties compared to high-precision extractions, the consistency with established values demonstrates that this framework can probe the left-hand-cut singularity.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2602.03115 [pdf]
2 citations

Affiliations

first authorsco-authorsvia INSPIRE