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Nuclear Theory·nucl-th

Monday·March 2, 2020

10 papers—5 primary·5 cross-listed

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  1. 06

    [Submitted on 27 Feb 2020] (cross-list from hep-ph)

    Influence of hadronic resonances on the chemical freeze-out in heavy-ion collisions

    P. Alba🇩🇪 · V. Mantovani Sarti🇩🇪 · J. Noronha-Hostler🇺🇸 · P. Parotto🇺🇸 · I. Portillo-Vazquez🇩🇪 · C. Ratti🇺🇸 · J. M. Stafford🇺🇸

    Detailed knowledge of the hadronic spectrum is still an open question, which has phenomenological consequences on the study of heavy-ion collisions. A previous lattice QCD study concluded that additional strange resonances are missing in the currently tabulated lists provided by the Particle Data Group (PDG). That study identified the list labeled PDG2016+ as the ideal spectrum to be used as an input in thermal-model-based analyses. In this work, we determine the effect of additional resonances on the freeze-out parameters of systems created in heavy-ion collisions. These parameters are obtained from thermal fits of particle yields and net-particle fluctuations. For a complete picture, we compare several hadron lists including both experimentally discovered and theoretically predicted states. We find that the inclusion of additional resonances mildly influences the extracted parameters -- with a general trend of progressively lowering the temperature -- but is not sufficient to close the gap in temperature between light and strange hadrons previously observed in the literature.

    Comments:
    13 pages, 8 figures, v2: typos corrected, references updated
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2002.12395 [pdf]
    PRC(2020)·52 citations
  2. 07

    [Submitted on 27 Feb 2020] (cross-list from hep-ph)

    The dijet mass distribution in heavy ion collisions

    Jared Reiten🇺🇸

    In these proceedings, we review the production of both light and heavy flavor dijets in heavy ion collisions and highlight a promising observable to expose their distinct signatures. We propose the modification of dijet invariant mass distributions in heavy ion collisions as a novel observable that exhibits striking sensitivity to the quark-gluon plasma transport properties and heavy quark mass effects on in-medium parton showers. This observable has the advantage of amplifying the effects of jet quenching in contrast to conventional observables, such as the dijet momentum imbalance shift, which involve cancellations of such effects and, hence, result in less pronounced signals. Predictions are presented for Au+Au collisions at = 200 GeV to guide the future sPHENIX program at the Relativistic Heavy Ion Collider.

    Comments:
    6 pages, 4 figures; Proceedings of the XLIX International Symposium on Multiparticle Dynamics
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2002.12442 [pdf]
    EPJ Web Conf.(2020)·0 citations
  3. 08

    [Submitted on 28 Feb 2020] (cross-list from hep-th)

    Fractal structure of Yang-Mills fields

    Airton Deppman🇧🇷 · Eugenio Megias🇪🇸 · Debora P. Menezes🇧🇷

    The origin of non-extensive thermodynamics in physical systems has been under intense debate for the last decades. Recent results indicate a connection between non-extensive statistics and thermofractals. After reviewing this connection, we analyze how scaling properties of Yang-Mills theory allow the appearance of self-similar structures in gauge fields. The presence of such structures, which actually behave as fractals, allows for recurrent non-perturbative calculations of vertices. It is argued that when a statistical approach is used, the non-extensive statistics is obtained, and the Tsallis entropic index, , is deduced in terms of the field theory parameters. The results are applied to QCD in the one-loop approximation, resulting in a good agreement with the value of obtained experimentally.

    Comments:
    12 pages, 4 figures. Talk given by E.Megias at the 8th International Conference on New Frontiers in Physics (ICNFP 2019), 21-29 Aug 2019, Kolymbari, Crete, Greece
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2002.12667 [pdf]
    Phys.Scripta(2020)·7 citations
  4. 09

    [Submitted on 28 Feb 2020] (cross-list from hep-ph)

    Charge-dependent flow induced by electromagnetic fields in heavy ion collisions

    U. Gürsoy🇳🇱 · D.E. Kharzeev🇺🇸 · E. Marcus🇳🇱 · K. Rajagopal🇺🇸 · C. Shen🇺🇸

    The colliding heavy ions create extremely strong magnetic and electric fields that significantly affect the evolution of the produced quark-gluon plasma (QGP). The knowledge of these fields is essential for establishing the role of topological fluctuations in the QGP through the chiral magnetic effect and related anomaly-induced phenomena. In this talk, we describe our work on the evolution of the QGP in electric and magnetic fields in the framework of hydrodynamics supplemented, in a perturbative fashion, by the dynamical electromagnetism. The evolution of the QGP fluid is described within the iEBE-VISHNU framework. We find that the electromagnetically induced currents result in a charge-odd directed flow and a charge-odd flow both of which are odd in rapidity. While the predicted magnitude of these charge-odd flows agrees with the data from RHIC and LHC, the sign of the predicted asymmetry between the flows of positive and negative hadrons is opposite to the data.

    Comments:
    4 pages, 3 figures, contribution to the proceedings of Quark Matter 2019 conference
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2002.12818 [pdf]
    NPA(2021)·4 citations
  5. 10

    [Submitted on 28 Feb 2020] (cross-list from astro-ph.HE)

    Redshift factor and diffusive equilibrium of unbound neutrons in the single nucleus model of accreting neutron star crust

    P.Haensel · J.L.Zdunik

    Using a Wigner-Seitz approximation with spherical cells, we re-analyze a widely used single nucleus model of accreting neutron star crust. We calculate beta disequilibrium within the crust, which is sizable, and implies that neutron and baryon chemical potentials, and , are not equal. We include also non-equilibrium reactions, driven by matter compression, and proceeding in the reaction layers. The constancy of , where the spacetime metric component , in the shells between the reaction layers is not applicable, because single electron captures are blocked, so that the neutron fraction is fixed, and therefore neutrons are not an independent component of the crust matter. The absence of neutron diffusion in the shells between the reaction layers, stems from the constancy of the neutron fraction (concentration) in these shells. In the reaction layers, the outward force resulting from neutron fraction gradient is balanced by the inward gravitational force acting on unbound neutrons. Neglecting the thickness of the reaction layers compared to the shell thickness, we obtain condition constant, where is Gibbs energy per nucleon, undergoing discontinuous drops on the reaction surfaces, and is a continuous function, due to the factor canceling the discontinuities (drops) in . The function is calculated using the Tolman-Oppenheimer-Volkov equations from and obtained from the equation of state (EOS) with discontinuites. The constancy of of is an extension of the standard relation constant, valid in hydrostatic equilibrium for catalyzed crust.

    Comments:
    To be submitted for publication. Remarks and comments on the present paper will be welcome by the authors
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2002.12827 [pdf]
    0 citations

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