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Nuclear Theory·nucl-th

Thursday·November 8, 2018

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 08

    [Submitted on 5 Nov 2018] (cross-list from hep-th)

    Skyrmions and clustering in light nuclei

    Carlos Naya🇬🇧 · Paul Sutcliffe🇬🇧

    One of the outstanding problems in modern nuclear physics is to determine the properties of nuclei from the fundamental theory of the strong force, quantum chromodynamics (QCD). Skyrmions offer a novel approach to this problem by considering nuclei as solitons of a low energy effective field theory obtained from QCD. Unfortunately, the standard theory of Skyrmions has been plagued by two significant problems, in that it yields nuclear binding energies that are an order of magnitude larger than experimental nuclear data, and it predicts intrinsic shapes for nuclei that fail to match the clustering structure of light nuclei. Here we show that extending the standard theory of Skyrmions, by including the next lightest subatomic meson particles traditionally neglected, dramatically improves both these aspects. We find Skyrmion clustering that now agrees with the expected structure of light nuclei, with binding energies that are much closer to nuclear data.

    Comments:
    5 pages, 3 figures. To appear in PRL
    Subjects:
    High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1811.02064 [pdf]
    PRL(2018)·68 citations
  2. 09

    [Submitted on 7 Nov 2018] (cross-list from hep-ph)

    The origin of the nucleon mass

    Cédric Lorcé (Ecole polytechnique, CPHT)🇫🇷

    It is often claimed that 98% of the nucleon mass is generated by quantum chromodynamics. The decomposition of the nucleon mass based on the trace of the energy-momentum tensor suggests that gluons play by far a dominant role. About 25 years ago, Ji proposed another decomposition based on the energy component of the energy-momentum tensor, leading to a quite different picture. Recently, we critically revisited these decompositions and argued that both overlooked pressure effects. In particular we showed that Ji's decomposition, although mathematically correct, makes little sense from a physical point of view. We identify the proper mass decomposition along with a balance equation for the pressure forces.

    Comments:
    6 pages, contribution to the proceedings of the XXII International Conference on Few-Body Problems in Physics (FB22) 2018, July 9-13, Caen, France
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1811.02803 [pdf]
    Springer Proc.Phys.(2020)·7 citations
  3. 10

    [Submitted on 7 Nov 2018] (cross-list from hep-ph)

    Doubly-heavy baryons, tetraquarks, and related topics

    Jean-Marc Richard🇫🇷 · Alfredo Valcarce🇪🇸 · Javier Vijande🇪🇸

    We review the physics of doubly-heavy baryons and tetraquarks . For the latter, the stability is reached for large enough mass ratio , even when spin forces and color mixing are neglected. It is thus customarily claimed that in its ground state cannot decay into . In some model, is shown to be stable if color mixing and spin effects are properly taken into account. It is conjectured that some benefits from favorable adjustments of the gluon tubes in the confinement regime. Some recent studies of pentaquarks and hexaquarks are also summarized.

    Comments:
    To appear in the Proc. of the Workshop "Double-Charm Baryons and Dimesons", Bled (Slovenia), June 17-23, 2018, ed. M.~Rosina et al
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1811.02863 [pdf]
    Bled Workshops Phys.(2018)·5 citations
  4. 11

    [Submitted on 7 Nov 2018] (cross-list from hep-ph)

    Chemical Equilibration in Hadronic Collisions

    Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪

    We study chemical equilibration in out-of-equilibrium Quark-Gluon Plasma using the first principles method of QCD effective kinetic theory, accurate at weak coupling. In longitudinally expanding systems--relevant for relativistic nuclear collisions--we find that for realistic couplings chemical equilibration takes place after hydrodynamization, but well before local thermalization. We estimate that hadronic collisions with final state multiplicities live long enough to reach approximate chemical equilibrium, which is consistent with the saturation of strangeness enhancement observed in proton-proton, proton-nucleus and nucleus-nucleus collisions.

    Comments:
    7 pages, 3 figures, see also our companion paper arXiv:1811.03068, v2 small changes, published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1811.03040 [pdf]
    PRL(2019)·103 citations
  5. 12

    [Submitted on 7 Nov 2018] (cross-list from hep-ph)

    Chemical Equilibration in Weakly Coupled QCD

    Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪

    We study thermalization, hydrodynamization, and chemical equilibration in out-of-equilibrium Quark-Gluon Plasma starting from various initial conditions using QCD effective kinetic theory, valid at weak coupling. In non-expanding systems gauge bosons rapidly lose information of the initial state and achieve kinetic equilibrium among themselves, while fermions approach the equilibrium distribution only at later time. In systems undergoing rapid longitudinal expansion, both gluons and quarks are kept away from equilibrium by the expansion, but the evolution is well described by fluid dynamics even before local thermal equilibrium is reached. For realistic couplings we determine the ordering between the separate hydrodynamization, chemical equilibration and thermalization time scales to be .

    Comments:
    11 pages, 9 figures, see also our companion paper arXiv:1811.03040 ; v2 minor changes, published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1811.03068 [pdf]
    PRD(2019)·104 citations

Affiliations

first authorsco-authorsvia INSPIRE