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Nuclear Theory·nucl-th

Tuesday·April 28, 2020

13 papers—8 primary·5 cross-listed

All13Primary8Cross-lists5
  1. 09

    [Submitted on 24 Apr 2020] (cross-list from hep-ph)

    Threshold Resummation for Hadron Production in the Small- Region

    Hao-Yu Liu🇨🇳 · Zhong-Bo Kang🇺🇸 · Xiaohui Liu🇨🇳

    We study the single hadron inclusive production in the forward rapidity region in proton-nucleus collisions. We find the long-standing negative cross section at next-to-leading-order (NLO) is driven by the large negative threshold logarithmic contributions. We established a factorization theorem for resumming these logarithms with systematically improvable accuracy within the color glass condensate formalism. We demonstrate how the threshold leading logarithmic accuracy can be realized by a suitable scale choice in the NLO results. The NLO spectrums with the threshold logarithms resummed remain positive and impressive agreements with experimental data are observed.

    Comments:
    6 pages, 3 figures, add comments on resummation and scale independence. Published in PRD as a rapid communication
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2004.11990 [pdf]
    PRD(2020)·38 citations
  2. 10

    [Submitted on 25 Apr 2020] (cross-list from nucl-ex)

    Modified Structure of Protons and Neutrons in Correlated Pairs

    B. Schmookler · M. Duer · A. Schmidt · O. Hen · S. Gilad · E. Piasetzky · M. Strikman · L.B. Weinstein · The CLAS Collaboration

    The atomic nucleus is made of protons and neutrons (nucleons), that are themselves composed of quarks and gluons. Understanding how the quark-gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification, known as the EMC effect, was first observed over 35 years ago, there is still no generally accepted explanation of its cause. Recent observations suggest that the EMC effect is related to close-proximity Short Range Correlated (SRC) nucleon pairs in nuclei. Here we report the first simultaneous, high-precision, measurements of the EMC effect and SRC abundances. We show that the EMC data can be explained by a universal modification of the structure of nucleons in neutron-proton (np) SRC pairs and present the first data-driven extraction of this universal modification function. This implies that, in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have its quark structure distorted.

    Comments:
    Published in Nature. Total: 21 pages, 9 figures, 10 tables. Main text: 7 pages, 4 figures. Methods section: 1 page. Extended Data: 1 figure, 3 table. Supplementary Materials: 11 pages, 4 figures, 7 tables
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2004.12065 [pdf]
    Nature(2019)·197 citations
  3. 11

    [Submitted on 25 Apr 2020] (cross-list from cond-mat.quant-gas)

    Bulk viscosity of resonating fermions revisited: Kubo formula, sum rule, and the dimer and high-temperature limits

    Keisuke Fujii · Yusuke Nishida

    The bulk viscosity of two-component fermions with a zero-range interaction is revisited both in two and three dimensions. We first point out that the "standard" Kubo formula employed in recent studies has flaws to give rise to an unphysical divergent bulk viscosity even in a limit where it is supposed to vanish. The corrected Kubo formula as well as the sum rule is then carefully rederived so as to confirm that the bulk viscosity indeed vanishes in the free, unitarity, and dimer limits. We also discuss that the recently found discrepancy between the Kubo formalism and the kinetic theory for the bulk viscosity is attributed to the fact that the quasiparticle approximation assumed by the latter breaks down even in the high-temperature limit.

    Comments:
    12 pages, 3 figures; published version
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
    arXiv:
    2004.12154 [pdf]
    PRA(2020)·15 citations
  4. 12

    [Submitted on 26 Apr 2020] (cross-list from hep-th)

    Symmetry restoration and the gluon mass in the Landau gauge

    Camille Noûs · Urko Reinosa · Julien Serreau · Rodrigo Carmo Terin · Matthieu Tissier

    We investigate the generation of a gluon screening mass in Yang-Mills theory in the Landau gauge. We propose a gauge-fixing procedure where the Gribov ambiguity is overcome by summing over all Gribov copies with some weight function. This can be formulated in terms of a local field theory involving constrained, nonlinear sigma model fields. We show that a phenomenon of radiative symmetry restoration occurs in this theory, similar to what happens in the standard nonlinear sigma model in two dimensions. This results in a nonzero gluon screening mass, as seen in lattice simulations.

    Comments:
    10 pages, 3 figures
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2004.12413 [pdf]
    SciPost Phys.(2021)·17 citations
  5. 13

    [Submitted on 27 Apr 2020] (cross-list from hep-th)

    Realistic classical binding energies in the -Skyrme model

    Sven Bjarke Gudnason🇨🇳 · James Martin Speight🇬🇧

    An omega-meson extension of the Skyrme model - without the Skyrme term but including the pion mass - first considered by Adkins and Nappi is studied in detail for baryon numbers 1 to 8. The static problem is reformulated as a constrained energy minimisation problem within a natural geometric framework and studied analytically on compact domains, and numerically on Euclidean space. Using a constrained second-order Newton flow algorithm, classical energy minimisers are constructed for various values of the omega-pion coupling. At high coupling, these Skyrmion solutions are qualitatively similar to the Skyrmions of the standard Skyrme model with massless pions. At sufficiently low coupling, they show similarities with those in the lightly bound Skyrme model: the Skyrmions of low baryon number dissociate into lightly bound clusters of distinct 1-Skyrmions, and the classical binding energies for baryon numbers 2 through 8 have realistic values.

    Comments:
    LaTeX: 42 pages, 10 figures; V2: comments and references added, typos corrected, summary of the model in explicit coordinates added in sec. 2.1
    Subjects:
    High Energy Physics — Theory (hep-th); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
    arXiv:
    2004.12862 [pdf]
    JHEP(2020)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE