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Nuclear Theory·nucl-th

Tuesday·November 18, 2025

11 papers—6 primary·5 cross-listed

All11Primary6Cross-lists5
  1. 01

    [Submitted on 14 Nov 2025]

    Coexisting phases in the chiral transition within the Linear sigma model with quarks

    R. M. Aguirre🇦🇷

    It is believed at present that the chiral transition changes from a smooth crossover to a first-order transition at low temperatures and high densities. Such regime is commonly analyzed using effective models since first principle calculations, as in lattice arrangements, are not feasible. This transition is assumed to be discontinuous, with unstable or metastable intermediate states. However, if multiple charges are simultaneously conserved the system could undergo a continuous change through a coexistence of equilibrium states. This type of transition has multiple manifestations, as in the nuclear liquid-gas transition causing the spinodal fragmentation. The coexistence of phases in the chiral transition is studied here for quark matter assuming the conservation of the isospin composition. Using the Linear sigma model with quarks several remarkable effects are found and discussed.

    Comments:
    Some figures updated, one reference corrected
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
    arXiv:
    2511.11822 [pdf]
    1 citation
  2. 02

    [Submitted on 14 Nov 2025]

    To bin or not to bin: does binning in multiplicity reliably suppress unwanted volume fluctuations?

    Bengt Friman🇩🇪 · Volker Koch🇺🇸

    In this study, we examine the effect of the so-called Centrality Bin Width Correction (CBWC) on the measurement of (net-)proton number cumulants in nucleus-nucleus collisions. We present an analytically tractable model, which includes correlations between multiplicity and proton number similar to those generated by the decay of baryon resonances. Within this model, we analyze the circumstances under which the CBWC method correctly removes the undesired effects of volume or impact parameter fluctuations. Additionally, we explore situations where the method fails and produces misleading results.

    Comments:
    21 pages, 6 figures, replaced by version published in Nuclear Physics A
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2511.11869 [pdf]
    4 citations
  3. 03

    [Submitted on 16 Nov 2025]

    Simplification of chiral nuclear forces near the unitarity limit

    Songlin Lyu🇨🇳 · Lin Zuo🇨🇳 · Rui Peng🇨🇳 · Sebastian König🇺🇸 · Bingwei Long🇨🇳

    Modern theory approaches for describing atomic nuclei often make use of on an effective theory that constructs the interaction between nucleons systematically based on Quantum Chromodynamics (QCD), exploiting constraints arising from the approximate chiral symmetry of QCD. The tensor nuclear force produced by one-pion exchange is an important feature that arises naturally in this framework. In this work we show that, however, the tensor force is suppressed by the large nucleon-nucleon scattering lengths in combination with the smallness of the pion mass. Based on this observation, we propose a new scheme for a chiral nuclear force that is able to describe phase shifts up to the center-of-mass momenta MeV while treating pion exchange as a perturbation. Our much simplified leading-order force provides a microscopic explanation for the recent success of various short-range nuclear forces from the perspective of chiral effective field theory, and it shares with those approaches an approximate Wigner SU(4) symmetry, as well as the closeness to the unitarity limit (infinite nucleon-nucleon scattering lengths), as guiding principles. Compared to previous approaches to perturbative-pion interactions, our force also adjusts the ordering of short-range contact interactions, by means of which we overcome convergence problems of the expansion that were previously assumed to severely limit its usefulness. We demonstrate the performance of our approach with numerical calculations of scattering up to fourth order, in addition to studies of and bound-state properties.

    Comments:
    11 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2511.12522 [pdf]
    3 citations
  4. 04

    [Submitted on 16 Nov 2025]

    Thermal Quarkyonic Matter and Its Implications for Neutron Star Structure

    K. Folias🇬🇷 · Ch.C. Moustakidis🇬🇷

    The structure and basic properties of dense nuclear matter still remain one of the open problems of Physics. In particular, the composition of the matter that composes neutron stars is under theoretical and experimental investigation. Among the theories that have been proposed, apart from the classical one where the composition is dominated by hadrons, the existence or coexistence of deconfined quark matter is a dominant guess. An approach towards this solution is the phenomenological view according to which the existence of quarkyonic matter plays a dominant role in the construction of the equation of state (EOS). According to it the structure of the EOS is based on the existence of the quarkyonic particle which is a hybrid state of a particle that combines properties of hadronic and quark matter with a corresponding representation in momentum space. In this paper we propose a phenomenological model for hot quarkyonic matter, borrowed from corresponding applications in hadronic models, where the interaction in the quarkyonic matter depends not only on the position but also on the momentum of the quarkyonic particles. This consideration, as we demonstrate, can have a remarkable consequence on the shape of the EOS and thus on the properties of neutron stars, especially in those for which the effect of temperature is significant, offering a sufficiently flexible model. Comparison with recent observational data can place constraints on the parameterization of the particular model and help improve its reliability.

    Comments:
    9 pages, 11 figures. Any comments are welcome
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2511.12669 [pdf]
    3 citations
  5. 05

    [Submitted on 17 Nov 2025]

    A deep learning approach for predicting multiple observables in Au+Au collisions at RHIC

    Jun-Qi Tao🇨🇳 · Xiang Fan🇨🇳 · Yang Liu🇨🇳 · Yu Sha🇨🇳 · Kai Zhou🇨🇳 · Hua Zheng🇨🇳 · Ben-Wei Zhang🇨🇳

    We develop a neural network model, based on the processes of high-energy heavy-ion collisions, to study and predict several experimental observables in Au+Au collisions. We present a data-driven deep learning framework for predicting multiple bulk observables in Au+Au collisions at RHIC energies. A single neural network is trained exclusively on experimental measurements of charged-particle pseudorapidity density distributions, transverse-momentum spectra and elliptic flow coefficients over a broad range of collision energies and centralities. The network architecture is inspired by the stages of a heavy-ion collision, from the quark-gluon plasma to chemical and kinetic freeze-out, and employs locally connected hidden layers and a structured input design that encodes basic geometric and kinematic features of the system. We demonstrate that these physics-motivated choices significantly improve test performance compared to purely fully connected baselines. The trained model is then used to predict the above observables at collision energies not yet explored experimentally at RHIC, and the results are validated using the energy dependence of the total charged-particle multiplicity per participant pair as well as comparisons to a CLVisc hydrodynamic calculation with TRENTo initial conditions. Our findings indicate that such physics-guided neural networks can serve as efficient surrogates to fill critical data gaps at RHIC and to support further phenomenological studies of QGP properties.

    Comments:
    12 pages, 14 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2511.13163 [pdf]
    PRC(2026)·0 citations
  6. 06

    [Submitted on 17 Nov 2025]

    Medium modification of the charge-weighted Energy-Energy Correlators in Pb+Pb collisions at ~TeV

    Han-Yao Liu · Shi-Yong Chen · Wei Dai · Ben-Wei Zhang

    We present a systematic study of medium-induced modifications in charge-dependent jet substructure using the charge-weighted Energy-Energy Correlators (EEC) in p+p and 0-10\% central Pb+Pb collisions at a center-of-mass energy of 5.02 TeV. Charged hadron jets as well as flavor separated quark and gluon-initiated jets with momentum 40-60 GeV and R=0.4 are analyzed. The ratio of the charge-weighted distribution to the inclusive EEC, which reflects the magnitude of charge correlations, is consistently negative, demonstrating the dominance of opposite-charge pairs due to charge conservation. In Pb+Pb collisions, significant medium modifications are observed. The A+A to p+p ratio for charge correlations exhibits a universal pattern across jet types, showing no flavor dependence. Jet quenching enhances opposite-charge correlations at small angles while reducing them at large angles, leading to a steeper angular distance RL dependence of charge correlations in A+A, indicating a more rapid decorrelation behavior as RL increases. A distinctive V-shaped modification pattern appears in the plateau-like enhancement in the transition and small-RL region, independent of jet flavor. Through factorization of the EEC into charged hadron pair multiplicity and average energy weighting distributions, we identify enhanced energy weighting of opposite-charge pairs at small RL as the origin of the V-shaped modification. Also, the plateau-like enhancement of charge correlations is found to be unrelated to selection bias effects.

    Comments:
    9 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2511.13495 [pdf]
    CPC(2026)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE