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Nuclear Theory·nucl-th

Monday·August 29, 2022

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    [Submitted on 26 Aug 2022]

    The lambda hyperon and the hyperon puzzle

    Wazha German🇧🇼 · Dr Jacobus Diener🇧🇼

    Neutron stars provide unique conditions to study cold dense nuclear matter at extreme densities. Due to these extreme conditions additional hadronic degrees of freedom are expected to be populated,including hyperons. This talk will focus on the influence of hyperons on the neutron star equation ofstate. In particular the contribution of the lambda hyperon will be discussed, as a first approximation to describing exotic neutron star equations of state. The system under consideration is where the strong nuclear force is described by the exchange of mesons and applying the relativistic mean field theory to study dense nuclear matter. As expected, the inclusion of the lambda hyperon softens the neutron star equation of state (EoS). A softer EoS will reduce the maximum mass attainable by the modeled neutron star with such EoS. While hyperons are certainly not unexpected in high density systems, but there presence seems to be contradicted by observations of high mass neutron stars. This contradiction is known as the "hyperon puzzle". The expected influx of observational data from massive new radio-telescopes like the Square Kilometer Array (SKA) will provide observations that can be supported and evolve theoretical models of nuclear matter. Therefore, the study of hyperonic matter is not only relevant to nuclear theory, but also locally to Botswana as an African partner country of the SKA.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2208.12514 [pdf]
    3 citations
  2. 02

    [Submitted on 26 Aug 2022]

    Probing nuclear observables via primordial nucleosynthesis

    Ulf-G. Meißner🇩🇪 · Bernard Ch. Metsch🇩🇪

    We study the dependence of primordial nuclear abundances on fundamental nuclear observables such as binding energies, scattering lengths, neutron lifetime, \textit{etc.} by varying these quantities. The numerical computations were performed with four publicly available codes, thus facilitating an investigation of the model-dependent (systematic) uncertainties on these dependences. Indeed deviations of the order of a few percent are found. Moreover, accounting for the temperature dependence of the sensitivity of the rates to some relevant parameters leads to a reduction of the sensitivity of the final primordial abundances, which in some cases is appreciable. These effects are considered to be relevant for studies of the dependence of the nuclear abundances on fundamental parameters such as quark masses or couplings underlying the nuclear parameters studied here.

    Comments:
    13 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    2208.12600 [pdf]
    EPJA(2022)·6 citations
  3. 03

    [Submitted on 26 Aug 2022]

    Rescattering effect on the measurement of K* spin alignment in heavy-ion collisions

    Ziyang Li🇨🇳 · Wangmei Zha🇨🇳 · Zebo Tang🇨🇳

    Spin alignment of vector mesons in noncentral relativistic heavy ion collisions provides a novel probe of the global quark polarization and hadronization mechanism. In this paper, we discuss the spin alignment of a short-lived vector meson, namely K*, arising from the hadronic rescattering process using the UrQMD model. This spin alignment is not related to global quark polarization but cannot be distinguished from those arising from global quark polarization in experiments. The spin alignment parameter is found to deviate from 1/3 by up to -0.008 (0.03) with respect to the reaction (production) plane. These deviations are much larger than the expected signal from all the theoretical models implementing the conventional global quark polarization mechanism as well as the current experimental precision, and should be considered seriously when comparing measurements with theoretical calculations.

    Comments:
    13 pages, 9 figures, accepted version
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2208.12750 [pdf]
    PRC(2022)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE