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Nuclear Theory·nucl-th

Friday·September 23, 2022

15 papers—7 primary·8 cross-listed

All15Primary7Cross-lists8
  1. 01

    [Submitted on 21 Sept 2022]

    Charge Symmetry Breaking Effects on Neutron Beta Decay in Non-Relativistic Quark Models

    Jacob W. Crawford🇺🇸 · Gerald A. Miller🇺🇸

    A formalism for the study of charge symmetry breaking (CSB) effects is discussed and used to analyze the effects of charge symmetry breaking on neutron beta decay. The effect of including CSB reduces the beta decay matrix element by an amount on the order of , a value much larger than the previous estimate. A much smaller contribution due to proton recoil is treated as well, which is found to be on the order of . The current uncertainty in the value of is also of order . An improvement of that uncertainty by an order of magnitude would require that charge symmetry breaking effects should be included in future analyses.

    Comments:
    8 pages, submitted to add citation
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2209.10603 [pdf]
    PRC(2022)·9 citations
  2. 02

    [Submitted on 22 Sept 2022]

    Pion superfluid phase transition under external magnetic field including inverse magnetic catalysis effect

    Shijun Mao🇨🇳 · Yvming Tian🇨🇳

    Pion superfluid phase transition under external magnetic field including the inverse magnetic catalysis (IMC) effect is investigated by the Pauli-Villars regularized NJL model. Based on the Goldstone's theorem, we apply the massless Goldstone boson ( meson) to determine the onset of pion superfluid phase. The inverse magnetic catalysis effect is introduced by the magnetic field dependent coupling , which is a decreasing function of magnetic field. At fixed temperature and baryon chemical potential, the critical isospin chemical potential for pion superfluid phase transition including IMC effect increases as the magnetic field grows, which is similar as the case without IMC effect. This demonstrates that magnetic field disfavors the pion superfluid phase when considering or ignoring IMC effect. The critical isospin chemical potential at fixed magnetic field, temperature and baryon chemical potential is shifted to higher value by the IMC effect. Since it is more difficult to form pion superfluid with weaker coupling.

    Comments:
    5 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2209.10738 [pdf]
    PRD(2022)·9 citations
  3. 03

    [Submitted on 22 Sept 2022]

    Microscopic description of the torque acting on fission fragments

    Guillaume Scamps

    When two fragments are created in a fission decay, any torque due to nuclear and Coulomb interaction can change the fragment's angular momentum. This article explores the character and magnitude of the angular momentum as a function of the initial conditions around the scission point using the time-dependent Hartree-Fock theory. To understand the torque acting on the fragments, the Frozen Hartree-Fock method is also used to determine the collective potential at scission. Two Pu fission channel ( Sn+Ru and Ba+Sr ) are studied. These two channels cover different shapes (spherical, quadrupole, and octupole deformation) of the fragments. It is found that the angular momentum generated by the Coulomb interaction after fission is mainly collective, while this is not the case for the angular momentum generated at scission. The competition between rotational modes (bending, wriggling, and twisting) is discussed and shows that the angular momentum is generated mainly perpendicular to the fission axis.

    Comments:
    8 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2209.10759 [pdf]
    PRC(2022)·18 citations
  4. 04

    [Submitted on 22 Sept 2022]

    Kaonic Hanbury-Brown-Twiss radii at 200 GeV and 5.02 TeV

    Mubarak Alqahtani🇸🇦 · Michael Strickland🇺🇸

    We use 3+1D quasiparticle anisotropic hydrodynamics (aHydroQP) to make predictions for kaon Hanbury-Brown-Twiss (HBT) radii in 200 GeV and 5.02 TeV heavy-ion collisions. Using previously determined aHydroQP parameters, we compute kaonic HBT radii and their ratios as a function of the mean transverse momentum of the pair . We first consider Au-Au collisions at 200 GeV, finding good agreement between aHydroQP predictions and experimental data up to GeV. We then present predictions for kaonic HBT radii and their ratios in 5.02 TeV Pb-Pb collisions. Our aHydroQP predictions do not exhibit a clear scaling of the pion and kaon source radii, however, an approximate transverse mass scaling is observed, particularly at 200 GeV.

    Comments:
    10 pages, 7 figures; v2 - major revision, published version
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2209.10894 [pdf]
    PRC(2023)·8 citations
  5. 05

    [Submitted on 22 Sept 2022]

    Effects of Initial Density Fluctuations on Cumulants in Au + Au Collisions at = 7.7 GeV

    Xiaoqing Yue🇨🇳 · Yongjia Wang🇨🇳 · Qingfeng Li🇨🇳 · Fuhu Liu🇨🇳

    Within the ultrarelativistic quantum molecular dynamics (UrQMD) model, the effect of initial density fluctuations on cumulants of the net-proton multiplicity distribution in Au + Au Collisions at = 7.7 GeV was investigated by varying the minimum distance between two nucleons in the initialization. It was found that the initial density fluctuations increased with the decrease of from 1.6 fm to 1.0 fm, and the influence of on the magnitude of the net-proton number fluctuation in a narrow pseudorapidity window ( 4) was negligible even if it indeed affected the density evolution during the collision. At a broad pseudorapidity window ( 4), the cumulant ratios were enlarged when the initial density fluctuations were increased with the smaller value of , and this enhancement was comparable to that observed in the presence of the nuclear mean-field potential. Moreover, the enhanced cumulants were more evident in collisions with a larger impact parameter. The present work demonstrates that the fingerprint of the initial density fluctuations on the cumulants in a broad pseudorapidity window is clearly visible, while it is not obvious as the pseudorapidity window becomes narrow.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2209.10923 [pdf]
    Universe(2022)·2 citations
  6. 06

    [Submitted on 21 Sept 2022]

    Cross effects in spin hydrodynamics: A revisit Entropy analysis and statistical operator

    Jin Hu🇨🇳

    We revisit the construction of first-order spin hydrodynamics and find that the constitution relations receive the corrections from the cross effects resulting from spin-orbit coupling. Starting from a routine entropy analysis, we show how to identify cross effects and new cross transport coefficients from the second law of thermodynamics. Interestingly, the conventional transport coefficient heat conductivity is bounded from below by the product of cross transport coefficients, which means the threshold of heat conduction is changed. With recourse to Zubarev's non-equilibrium statistical operator, we reproduce the construction of first-order spin hydrodynamics and identification of cross effects in a more rigorous way. By seeking the dispersion relations of normal modes, we find that these cross effects suppress the attenuation of sound modes and heat mode appearing in conventional hydrodynamics and also have impacts on the damping of non-hydrodynamic spin modes.

    Comments:
    The version published in PRC
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2209.10979 [pdf]
    PRC(2023)·23 citations
  7. 07

    [Submitted on 22 Sept 2022]

    Chiral restoration of strange baryons

    Eduardo S. Fraga🇧🇷 · Rodrigo da Mata🇧🇷 · Savvas Pitsinigkos🇬🇧 · Andreas Schmitt🇬🇧

    We review the results of a phenomenological model for cold and dense nuclear matter exhibiting a chiral phase transition. The idea is to model the quark-hadron phase transition under neutron star conditions within a single model, but without adding quark degrees of freedom by hand. To this end, strangeness is included in the form of hyperonic degrees of freedom, whose light counterparts provide the strangeness in the chirally restored phase. In the future, the model can be used for instance to compute the surface tension at the (first-order) chiral phase transition and to study the possible existence of inhomogeneous phases.

    Comments:
    6 pages, 4 figures, contribution to proceedings of QCD@Work, 27-30 June 2022
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2209.10980 [pdf]
    EPJ Web Conf.(2022)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE