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Nuclear Theory·nucl-th

Monday·July 16, 2018

18 papers—12 primary·6 cross-listed

All18Primary12Cross-lists6
  1. 13

    [Submitted on 12 Jul 2018] (cross-list from nucl-ex)

    Measurements of directed and elliptic flow for and mesons using the STAR detector at RHIC

    Subhash Singha (for the STAR Collaboration)🇺🇸

    We report on the first evidence for a non-zero rapidity-odd directed flow () for and mesons in 10-80\% centrality Au+Au collisions at = 200~GeV measured with the STAR detector at RHIC. The slope of the rapidity dependence () averaged over and mesons is -0.081 0.021 0.017, while that of charged kaons is -0.0030 0.0001 0.0002, suggesting significantly larger slope for the mesons. Models indicate that the large of mesons is sensitive to the initially tilted source. We also present a new measurement of the meson elliptic flow () as a function of transverse momentum () in Au+Au collisions at = 200~GeV with an improved precision with respect to the previously published results.The results are compared to those of light-flavor hadrons to test the number-of-constituent-quark (NCQ) scaling. Both the and results are compared to recent hydrodynamic and transport model calculations.

    Comments:
    4 pages, 4 figures. Submitted in Quark Matter 2018 proceedings (accepted for publication in Nuclear Physics A)
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.04771 [pdf]
    NPA(2019)·7 citations
  2. 14

    [Submitted on 13 Jul 2018] (cross-list from hep-ph)

    In-medium spectral functions and dilepton rates with the Functional Renormalization Group

    Ralf-Arno Tripolt🇮🇹 · Christopher Jung🇩🇪 · Naoto Tanji🇮🇹 · Lorenz von Smekal🇩🇪 · Jochen Wambach🇮🇹

    We present recent results on in-medium spectral functions of vector and axial-vector mesons, the electromagnetic (EM) spectral function and dilepton rates using the Functional Renormalization Group (FRG) approach. Our method is based on an analytic continuation procedure that allows us to calculate real-time quantities like spectral functions at finite temperature and chemical potential. As an effective low-energy model for Quantum Chromodynamics (QCD) we use an extended linear-sigma model including quarks where (axial-)vector mesons as well as the photon are introduced as gauge bosons. In particular, it is shown how the and the spectral function become degenerate at high temperatures or chemical potentials due to the restoration of chiral symmetry. Preliminary results for the EM spectral function and the dilepton production rate are discussed with a focus on the possibility to identify signatures of the chiral crossover and the critical endpoint (CEP) in the QCD phase diagram.

    Comments:
    Quark Matter 2018 proceedings
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.04952 [pdf]
    NPA(2019)·23 citations
  3. 15

    [Submitted on 13 Jul 2018] (cross-list from hep-ph)

    Nonequilibrium quark production in the expanding QCD plasma

    Naoto Tanji🇮🇹 · Juergen Berges🇩🇪

    We present real-time lattice simulation results for nonequilibrium quark production from an over-occupied gluon plasma in longitudinally expanding geometry. The quark number density per unit transverse area and rapidity shows almost linear growth in time, and its growth rate appears to be consistent with a simple kinetic theory estimate involving only two-to-two scattering processes in small-angle approximation. We also find that quarks produced at early times satisfy a nonequilibrium scaling law.

    Comments:
    Quark Matter 2018 proceedings
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.05033 [pdf]
    NPA(2019)·1 citation
  4. 16

    [Submitted on 12 Jul 2018] (cross-list from nucl-ex)

    Status of the Chiral Magnetic Effect Search in Relativistic Heavy-Ion Collisions

    Jie Zhao🇨🇳 · Zhoudunming Tu🇺🇸 · Fuqiang Wang🇨🇳

    Quark interactions with topological gluon fields in QCD can yield local and violations which could explain the matter-antimatter asymmetry in our universe. Effects of and violations can result in charge separation under a strong magnetic field, a phenomenon called the chiral magnetic effect (CME). Experimental measurements of the CME-induced charge separation in heavy-ion collisions are dominated by physics backgrounds. Major theoretical and experimental efforts have been devoted to eliminating or reducing those backgrounds. We review the current status of these efforts in the search for the CME in heavy-ion collisions.

    Comments:
    17 pages, 22 figures, invited review by Nuclear Physics Review. arXiv admin note: substantial text overlap with arXiv:1805.02814
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.05083 [pdf]
    Nucl.Phys.Rev.(2018)·26 citations
  5. 17

    [Submitted on 13 Jul 2018] (cross-list from hep-ph)

    Forward rapidity isolated photon production in proton-nucleus collisions

    B. Ducloué🇫🇷 · T. Lappi🇫🇮 · H. Mäntysaari🇫🇮

    We calculate isolated photon production at forward rapidities in proton-nucleus collisions in the Color Glass Condensate framework. Our calculation uses dipole cross sections solved from the running coupling Balitsky-Kovchegov equation with an initial condition fit to deep inelastic scattering data and extended to nuclei with an optical Glauber procedure that introduces no additional parameters beyond the basic nuclear geometry. We present predictions for future forward RHIC and LHC measurements. The predictions are also compared to updated results for the nuclear modification factors for pion production, Drell-Yan dileptons and mesons in the same forward kinematics, consistently calculated in the same theoretical framework. We find that leading order, running coupling high energy evolution in the CGC picture leads to a significant nuclear suppression at forward rapidities. This nuclear suppression is stronger for photons than for pions. We also discuss how this might change with next-to-leading order high energy evolution.

    Comments:
    4 pages, 4 figures, talk by T.L. at the Quark Matter 2018 conference
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.05094 [pdf]
    NPA(2019)·0 citations
  6. 18

    [Submitted on 13 Jul 2018] (cross-list from hep-th)

    Holographic Collisions across a Phase Transition

    Maximilian Attems🇪🇸 · Yago Bea🇪🇸 · Jorge Casalderrey-Solana🇪🇸 · David Mateos🇪🇸 · Miquel Triana🇪🇸 · Miguel Zilhao🇵🇹

    We use holography to analyse relativistic collisions in a one-parameter family of strongly coupled gauge theories with thermal phase transitions. For a critical value of the parameter the transition is second order, for subcritical values it is first order, and for super-critical values it is a smooth crossover. We extract the gauge theory stress tensor from collisions of gravitational shock waves on the dual geometries. Regardless of the nature of the transition, for values of the parameter close to the critical value almost all the energy of the projectiles is deposited into a long-lived, quasi-static blob of energy at mid-rapidity. This configuration is well described by the constitutive relations of second-order hydrodynamics that include all second-order gradients that are purely spatial in the local rest frame. In contrast, a Müller-Israel-Stewart-type formulation of hydrodynamics fails to provide a good description. We discuss possible implications for searches of the QCD critical point.

    Comments:
    6 pages, 3 figures
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.05175 [pdf]
    PRL(2018)·59 citations

Affiliations

first authorsco-authorsvia INSPIRE