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Nuclear Theory·nucl-th

Friday·February 20, 2026

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 05

    [Submitted on 19 Feb 2026] (cross-list from hep-lat)

    Quarkonium in non-zero isospin chemical potential environment at

    Seyong Kim🇰🇷 · Bastian B. Brandt🇩🇪 · Gergely Endrődi🇭🇺

    We study how the isospin asymmetry affects quarkonium states in QCD at near zero temperature. Using lattice Non-Relativistic QCD formalism, we calculate bottom quark correlators in the gauge field ensembles generated with flavors of dynamical staggered quarks whose dynamics include the isospin chemical potential effect and then construct and wave quarkonium state correlators. From these quarkonium correlators, we consider the ratios of quarkonium correlators at non-zero isospin chemical potential to that at . Here, the gauge field ensemble with and on a lattice with non-zero isospin current strength and , where MeV and fm from \cite{Brandt:2022hwy}, are used. Preliminary results suggest that for , the Upsilon mass gets heavier than the Upsilon mass in the vacuum and that below the isospin asymmetry effect on the Upsilon mass is not monotonic.

    Comments:
    10 pages, 13 figures, 1 table, Proceedings of the 42nd International Symposium on Lattice Field Theory (Lattice 2025), TIFR Mumbai, India, 2025
    Subjects:
    High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2602.17232 [pdf]
    0 citations
  2. 06

    [Submitted on 19 Feb 2026] (cross-list from cond-mat.quant-gas)

    Hartree shift and pairing gap in ultracold Fermi gases in the framework of low-momentum interactions

    Michael Urban🇫🇷 · S. Ramanan🇮🇳

    In this paper we consider a two-component gas of fermions on the BCS side of the BCS-BEC crossover at zero temperature. We use a momentum dependent interaction that reproduces the s-wave scattering phase shifts of a contact interaction up to a momentum cutoff that is scaled with the Fermi momentum. Using a diagrammatic formulation of Bogoliubov many-body perturbation theory, suitably augmented by self-consistency conditions, we obtain the Hartree shift and the pairing gap to third order. In the weak-coupling regime, our results are not only well-converged but also agree with the well-established Gor'kov-Melik-Barkhudarov corrections for the gap and the Galitskii result for the Hartree shift. Near the unitary regime, our results for the Nambu-Gor'kov self-energy are less converged, but there is still reasonable agreement with experiments as well as with quantum Monte-Carlo results. Perspectives for improvements and applications of this approach to neutron matter are discussed.

    Comments:
    15 pages, 10 figures; v2: minor changes
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
    arXiv:
    2602.17420 [pdf]
    PRA(2026)·1 citation
  3. 07

    [Submitted on 19 Feb 2026] (cross-list from hep-ph)

    Chiral symmetry restoration effects onto the meson spectrum from a Dyson-Schwinger and Bethe-Salpeter approach

    Reinhard Alkofer🇦🇹 · Christian S. Fischer🇩🇪 · Fabian Zierler🇩🇪

    Light meson spectra are studied in a Dyson-Schwinger/Bethe-Salpeter approach to QCD. By varying the interaction strength of three sets of models for the quark-antiquark interaction, the transition from the chiral symmetric to the chirally broken regime in the vacuum is studied. The simplest type of these models leads to degenerate meson spectra for a large domain of the strength parameter. The more sophisticated and thus more realistic models show significantly smaller parameter domains for which degenerate meson spectra are obtained. The underlying mechanism for obtaining and then lifting degeneracies is traced back to the location of the quark propagators' poles, in particular, whether they are beyond or within the domain of integration in the Bethe-Salpeter equation. In view of this mechanism the potential relation of the obtained degeneracies to the dynamical emergence of symmetries is discussed, adding thereby another point of view on the conjectured chiral spin symmetry of QCD in the temperature domain right above the crossover.

    Comments:
    12 pages, 7 figures, 3 tables; matches published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2602.17456 [pdf]
    PRD(2026)·5 citations
  4. 08

    [Submitted on 19 Feb 2026] (cross-list from hep-ph)

    Hyperon longitudinal polarization and vector meson spin alignment in a thermal model for heavy-ion collisions

    Soham Banerjee🇮🇳 · Samapan Bhadury🇮🇳 · Wojciech Florkowski🇵🇱 · Amaresh Jaiswal🇮🇳 · Radoslaw Ryblewski🇵🇱

    The concept of a common local spin equilibrium for both spin-1/2 and spin-1 particles is incorporated into a thermal model of particle production in heavy-ion collisions at the top RHIC energies. We show that an effective spin polarization tensor leading to a correct description of the longitudinal spin polarization of hyperons simultaneously yields a positive alignment of vector mesons ( and ) that grows monotonically with transverse momentum and centrality. Similar trends can be seen in the data, suggesting a possible common mechanism for longitudinal spin polarization and alignment. However, model calculations are insufficient to explain the data in a fully quantitative way. The correlation found between the magnitude of the longitudinal polarization and vector meson alignment suggests further more elaborate investigations of this issue.

    Comments:
    16 pages, 6 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2602.17500 [pdf]
    Acta Phys.Polon.B(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE