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Nuclear Theory·nucl-th

Tuesday·February 18, 2020

14 papers—8 primary·6 cross-listed

All14Primary8Cross-lists6
  1. 09

    [Submitted on 15 Feb 2020] (cross-list from astro-ph.HE)

    The gluon condensation effect in the cosmic hadron spectra

    W. Zhu🇨🇳 · P. Liu🇨🇳 · J.H. Ruan🇨🇳 · R.Q. Wang🇨🇳 · F. Wang🇨🇳

    Hardening of cosmic proton- and nuclei-spectra is explained by using the gluon condensation (GC) model, which states that a large amount of gluons in proton may condense near the high energy threshold. The results present the GC-effect as common origin of a series of anomalous astrophysical phenomena including the broken power-law in gamma-ray spectra, the excess in positron- and electron-spectra and hardening of proton- and nuclei-spectra.

    Comments:
    25 pages, 9 figures; accepted for publication in JCAP
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2002.06294 [pdf]
    JCAP(2020)·5 citations
  2. 10

    [Submitted on 15 Feb 2020] (cross-list from hep-ph)

    Interplaying mechanisms behind inclusive jet and extraction of jet energy loss distributions

    Y. He (1)🇨🇳 · S. Cao (2)🇺🇸 · W. Chen (1)🇨🇳 · T. Luo (1)🇨🇳 · L.-G. Pang (3 and 4)🇺🇸 · X.-N. Wang (1, 3 and 4) ((1) Central China Normal University, (2) Wayne State University, (3) University of California, Berkeley, (4) Lawrence Berkeley National Laboratory)🇨🇳

    The observed inclusive jet suppression in heavy-ion collisions at LHC has a very weak dependence over a large range of = 50-1000 GeV and is almost independent of the colliding energy, though the initial energy density of the bulk medium has increased from = 2.76 to 5.02 TeV by about 20%. This interesting phenomenon is investigated in the linear Boltzmann transport (LBT) model for jet propagation in an event-by-event 3+1D hydro background. We show that the dependence of jet is determined by the initial spectrum in collisions and dependence of jet energy loss. Furthermore, jet energy loss distributions for inclusive jet and jet at both LHC energies are extracted directly from experimental data through the state-of-art Bayesian analysis. The averaged jet energy loss has a weak dependence and the scaled jet energy loss distributions have a large width, both of which are consistent with the LBT simulations and indicate that jet quenching is caused by only a few out-of-cone jet medium scatterings.

    Comments:
    4 pages, 3 figures, contribution to the proceedings of XXVIIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2019)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2002.06411 [pdf]
    NPA(2021)·1 citation
  3. 11

    [Submitted on 15 Feb 2020] (cross-list from astro-ph.HE)

    Constraints on the muon fraction and density profile in neutron stars

    Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸

    Muons in neutron stars (NSs) play especially important roles in addressing several interesting new physics questions associated with detecting as well as understanding interactions and astrophysical effects of muonphilic dark matter particles. The key model inputs for studying the latter are the total muon mass , the muon mass fraction over the NS mass and the muon radial density profile in NSs of varying masses. We investigate these quantities within a minimum model for the core of NSs consisting of neutrons, protons, electrons, and muons using an explicitly isospin-dependent parametric Equation of State (EOS) constrained by available nuclear laboratory experiments and the latest astrophysical observations of NS masses, radii and tidal deformabilities. We found that the absolutely maximum muon mass and its mass fraction in the most massive NSs allowed by causality are about 0.025 and 1.1\%, respectively. For the most massive NS of mass 2.14 observed so far, they reduce to about 0.020 and 0.9\%, respectively. We also study respective effects of individual parameters describing the EOS of high-density neutron-rich nucleonic matter on the muon contents in NSs with varying masses. We found that the most important but uncertain nuclear physics ingredient for determining the muon contents in NSs is the high-density nuclear symmetry energy.

    Comments:
    Added more discussions and references. The Astrophysical Journal (2020) in press
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2002.06446 [pdf]
    ApJ(2020)·38 citations
  4. 12

    [Submitted on 17 Feb 2020] (cross-list from hep-ph)

    Jet quenching parameters in strongly coupled anisotropic plasmas in the presence of magnetic fields

    Romulo Rougemont (Rio de Janeiro State U.)🇧🇷

    I use the holographic gauge/gravity duality to systematically calculate the jet quenching parameters in strongly coupled anisotropic plasmas in the presence of external magnetic fields. The magnetic field breaks down spatial rotation symmetry from to , leading to the presence of multiple anisotropic jet quenching parameters, which are evaluated here in two quite different holographic settings. One of them corresponds to a top-down deformation of the strongly coupled Super Yang-Mills plasma triggered by an external magnetic field, while the other one is a bottom-up Einstein-Maxwell-Dilaton model of phenomenological relevance for high energy peripheral heavy ion collisions, since it is able to provide a quantitative description of -flavors lattice QCD thermodynamics with physical quark masses at zero and nonzero magnetic fields. I find for both models an overall enhancement of all the anisotropic jet quenching parameters with increasing magnetic fields. Moreover, I also conclude that for both models transverse momentum broadening is larger in transverse directions than in the direction of the magnetic field. Since these conclusions are shown to hold for two rather different holographic setups at finite temperature and magnetic fields, they are suggested as fairly robust features of strongly coupled anisotropic magnetized plasmas.

    Comments:
    28 pages, 3 figures, accepted for publication in Physical Review D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2002.06725 [pdf]
    PRD(2020)·19 citations
  5. 13

    [Submitted on 17 Feb 2020] (cross-list from hep-lat)

    Non-perturbative definition of the QCD energy-momentum tensor on the lattice

    Mattia Dalla Brida🇮🇹 · Leonardo Giusti🇮🇹 · Michele Pepe🇮🇹

    We present a strategy to define non-perturbatively the energy-momentum tensor in Quantum Chromodynamics (QCD) which satisfies the appropriate Ward identities and has the right trace anomaly. The tensor is defined by regularizing the theory on a lattice, and by fixing its renormalization constants non-perturbatively by suitable Ward identities associated to the Poincare' invariance of the continuum theory. The latter are derived in thermal QCD with a non-zero imaginary chemical potential formulated in a moving reference frame. A renormalization group analysis leads to simple renormalization-group-invariant definitions of the gluonic and fermionic contributions to either the singlet or the non-singlet components of the tensor, and therefore of their form factors among physical states. The lattice discussion focuses on the Wilson discretization of quark fields but the strategy is general. Specific to that case, we also carry out the analysis for the on-shell O(a)-improvement of the energy-momentum tensor. The renormalization and improvement programs profit from the fact that, as shown here, the thermal theory enjoys de-facto automatic O(a)-improvement at finite temperature. The validity of the proposal is scrutinized analytically by a study to 1-loop order in lattice perturbation theory with shifted and twisted (for quarks only) boundary conditions. The latter provides also additional useful insight for a precise non-perturbative calculation of the renormalization constants. The strategy proposed here is accessible to Monte Carlo computations, and in this sense it provides a practical way to define non-perturbatively the energy-momentum tensor in QCD.

    Comments:
    Final version to appear on JHEP. Minor modifications in sections 2 and 5. One reference added
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2002.06897 [pdf]
    JHEP(2020)·37 citations
  6. 14

    [Submitted on 17 Feb 2020] (cross-list from hep-lat)

    Model-independent determination of the nucleon charge radius from lattice QCD

    Constantia Alexandrou🇨🇾 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Konstantin Ottnad🇩🇪 · Marcus Petschlies🇩🇪

    Lattice QCD calculations of nucleon form factors are restricted to discrete values of the Euclidean four-momentum transfer. Therefore, the extraction of radii typically relies on parametrizing and fitting the lattice QCD data to obtain its slope close to zero momentum transfer. We investigate a new method, which allows to compute the nucleon radius directly from existing lattice QCD data, without assuming a functional form for the momentum dependence of the underlying form factor. The method is illustrated for the case of the isovector mean square charge radius of the nucleon and the quark-connected contributions to and for the proton and neutron, respectively. Computations are performed using a single gauge ensemble with maximally twisted mass clover-improved fermions at physical quark mass and a lattice spacing of .

    Comments:
    19 pages, 9 figures and 2 tables, matching version accepted for publication in PRD
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2002.06984 [pdf]
    PRD(2020)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE