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Nuclear Theory·nucl-th

Wednesday·February 4, 2026

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 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
  2. 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
  3. 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
  4. 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
  5. 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 and channels. The amplitude zero for the center-of-mass momentum near 0.35 GeV in the channel is naturally accommodated within this framework. We extract the pole position, scattering length, effective range, and the pseudoscalar pion-nucleon coupling constant at different expansion orders. The low-energy parameters are stable and consistent with established values, while exhibits larger uncertainties. The extraction of 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