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Nuclear Theory·nucl-th

Tuesday·October 19, 2021

15 papers—6 primary·9 cross-listed

All15Primary6Cross-lists9
  1. 01

    [Submitted on 16 Oct 2021]

    Protonium annihilation densities in a unitary coupled channel model

    Emanuel Ydrefors🇧🇷 · Jaume Carbonell🇫🇷

    We consider a unitary coupled channel model to describe the low energy proton-antiproton scattering and the lower Coulomb-like protonium states. The existence of deeper quasi-bound states of nuclear nature is found to be a consequence of the experimental data. The properties of these states as well as the protonium annihilation densities are described and the difference with respect to the optical models description are manifested.

    Comments:
    14 pages
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2110.08628 [pdf]
    EPJA(2021)·4 citations
  2. 02

    [Submitted on 17 Oct 2021]

    Hybrid stars with color superconducting cores in an extended FCM model

    Daniela Curin🇦🇷 · Ignacio F. Ranea-Sandoval🇦🇷 · Mauro Mariani🇦🇷 · Milva G. Orsaria🇦🇷 · Fridolin Weber🇺🇸

    We investigate the influence of repulsive vector interactions and color superconductivity on the structure of neutron stars using an extended version of the field correlator method (FCM) for the description of quark matter. The hybrid equation of state is constructed using the Maxwell description, which assumes a sharp hadron-quark phase transition. The equation of state of hadronic matter is computed for a density-dependent relativistic lagrangian treated in the mean-field approximation, with parameters given by the SW4L nuclear model. This model described the interactions among baryons in terms of , and mesons. Quark matter is assumed to be in either the CFL or the 2SC+s color superconducting phase. The possibility of sequential (hadron-quark, quark-quark) transitions in ultra-dense matter is investigated. Observed data related to massive pulsars, gravitational-wave events, and NICER are used to constrain the parameters of the extended FCM model. The successful equations of state are used to explore the mass-radius relationship, radii, and tidal deformabilities of hybrid stars. A special focus lies on investigating consequences that slow or fast conversions of quark-hadron matter have on the stability and the mass-radius relationship of hybrid stars. We find that if slow conversion should occur, a new branch of stable massive stars would exist whose members have radii that are up to 1.5~km smaller than those of conventional neutron stars of the same mass. Such objects could be possible candidates for the stellar high-mass object of the GW190425 binary system.

    Comments:
    This article has the same content as the one published in Universe 2021, 7(10), 370
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)
    arXiv:
    2110.08892 [pdf]
    Universe(2021)·12 citations
  3. 03

    [Submitted on 17 Oct 2021]

    Low Density Neutron Star Matter with Quantum Molecular Dynamics: The Role of Vector Interactions

    Parit Mehta · Rana Nandi · R. O. Gomes · V. Dexheimer · J. Steinheimer

    The effect of isospin-dependent nuclear forces on the inner crust of neutron stars is modeled within the framework of Quantum Molecular Dynamics (QMD). To successfully control the density dependence of the symmetry energy of neutron-star matter below nuclear saturation density, a coupling potential between the and meson fields is introduced. This approach is inspired by the baryon density and isospin density-dependent repulsive Skyrme force of asymmetric nuclear matter. In isospin-asymmetric nuclear matter, the system shows nucleation, as nucleons are arranged into shapes resembling nuclear pasta. The dependence of clusterization in the system on the isospin properties is also explored by calculating two-point correlation functions. We show that, as compared to previous results that did not involve the - potential, the energy symmetry slope is successfully controlled by varying the - coupling strength. Nevertheless, the effect of changing the slope of the nuclear symmetry energy on the crust-core transition density does not seem significant. To the knowledge of the authors, This is the first implementation of a - coupling in a QMD model for the inner crust of neutron stars.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2110.08916 [pdf]
    Universe(2022)·4 citations
  4. 04

    [Submitted on 18 Oct 2021]

    Strange quark matter and proto-strange stars in an equivaparticle model

    H. M. Chen🇨🇳 · C. J. Xia🇨🇳 · G. X. Peng🇨🇳

    The properties of strange quark matter and the structures of (proto-)strange stars are studied within the framework of an equivparticle model, where a new quark mass scaling and self-consistent thermodynamic treatment are adopted. Our results show that the perturbative interaction has a strong impact on the properties of strange quark matter. It is found that the energy per baryon increases with temperature, while the free energy decreases and eventually becomes negative. At fixed temperatures, the pressure at the minimum free energy per baryon is zero, suggesting that the thermodynamic self-consistency is preserved. Additionally, the sound velocity v in quark matter approaches to the extreme relativistic limit (c/sqrt(3)) as the density increases. By increasing the strengths of confinement parameter D and perturbation parameter C, the tendency for v to approach the extreme relativistic limit at high density is slightly weakened. For (proto-)strange stars, in contrast to the quark mass scalings adopted in previous publications, the new quark mass scaling can accommodate massive proto-strange stars with their maximum mass surpassing twice the solar mass at T = 50 MeV.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2110.09187 [pdf]
    CPC(2022)·8 citations
  5. 05

    [Submitted on 18 Oct 2021]

    Importance truncation for the in-medium similarity renormalization group

    J. Hoppe · A. Tichai · M. Heinz · K. Hebeler · A. Schwenk

    Ab initio nuclear many-body frameworks require extensive computational resources, especially when targeting heavier nuclei. Importance-truncation (IT) techniques allow to significantly reduce the dimensionality of the problem by neglecting unimportant contributions to the solution of the many-body problem. In this work, we apply IT methods to the nonperturbative in-medium similarity renormalization group (IMSRG) approach and investigate the induced errors for ground-state energies in different mass regimes based on different nuclear Hamiltonians. We study various importance measures, which define the IT selection, and identify two measures that perform best, resulting in only small errors to the full IMSRG(2) calculations even for sizable compression ratios. The neglected contributions are accounted for in a perturbative way and serve as an estimate of the IT-induced error. Overall we find that the IT-IMSRG(2) performs well across all systems considered, while the largest compression ratios for a given error can be achieved when using soft Hamiltonians and for large single-particle bases.

    Comments:
    14 pages, 9 figures, published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2110.09390 [pdf]
    PRC(2022)·8 citations
  6. 06

    [Submitted on 18 Oct 2021]

    Freezeout properties of different light nuclei at the RHIC Beam Energy Scan

    M. Waqas🇨🇳 · G. X. Peng🇨🇳 · Rui-Qin Wang🇨🇳 · Muhammad Ajaz🇵🇰 · Abd Al Karim Haj Ismail🇦🇪

    We study the transverse momentum spectra of light nuclei (deuteron, anti-deuteron and triton) produced in Gold-Gold (Au-Au) collisions in different centrality bins by the blast wave model with Tsallis statistics. The model results are in agreement with the experimental data measured by STAR Collaboration in special transverse momentum ranges. We extracted the kinetic freezeout temperature, transverse flow velocity and kinetic freezeout volume. It is observed that kinetic freezeout temperature and transverse flow velocity increases initially, and then saturates from 14.5-39 GeV, while the kinetic freezeout volume increase initially up to 19.6 GeV but saturates from 19.6-39 GeV. This may indicate that the phase transition starts in part volume that ends in the whole volume at 39 GeV and the critical point may exists somewhere in the energy range of 14.5-39 GeV. The present work observed that the kinetic freezeout temperature, transverse flow velocity and kinetic freezeout volume has a decreasing trend from central to peripheral collisions. We found the freezeout volume of triton is smaller than those of deuteron and anti-deuteron, which shows that triton freezeout earlier than that of deuteron and anti-deuteron.

    Comments:
    21 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2110.09505 [pdf]
    Eur.Phys.J.Plus(2021)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE