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Nuclear Theory·nucl-th

Thursday·March 2, 2017

5 papers—2 primary·3 cross-listed

All5Primary2Cross-lists3
  1. 01

    [Submitted on 1 Mar 2017]

    Photons from the Early Stages of Relativistic Heavy Ion Collisions

    L. Oliva🇮🇹 · M. Ruggieri🇨🇳 · S. Plumari🇮🇹 · F. Scardina🇮🇹 · G. X. Peng🇨🇳 · V. Greco🇮🇹

    We present results about photons production in relativistic heavy ion collisions. The main novelty of our study is the calculation of the contribution of the early stage photons to the photon spectrum. The initial stage is modeled by an ensemble of classical gluon fields which decay to a quark-gluon plasma via the Schwinger mechanism, and the evolution of the system is studied by coupling classical field equations to relativistic kinetic theory; photons production is then computed by including the pertinent collision processes into the collision integral. We find that the contribution of the early stage photons to the direct photon spectrum is substantial for GeV and higher, the exact value depending on the collision energy; therefore we identify this part of the photon spectrum as the sign of the early stage. Moreover, the amount of photons produced during the early stage is not negligible with respect to those produced by a thermalized quark-gluon plasma: we support the idea that there is no dark age in relativistic heavy ion collisions.

    Comments:
    11 pages, 9 figures. Matches published version
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1703.00116 [pdf]
    PRC(2017)·27 citations
  2. 02

    [Submitted on 28 Feb 2017]

    Repulsive interactions and their effects on the thermodynamics of hadron gas

    Pok Man Lo🇵🇱 · Bengt Friman🇩🇪 · Michal Marczenko🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱

    We compare two approaches in modeling repulsive interactions among hadrons: the excluded volume approximation and the S-matrix formalism. These are applied to study the thermodynamics of the system. It is shown that the introduction of an extraneous repulsion between pions and nucleons via the excluded volume approach, in addition to the interaction that generates the -resonance, is incompatible with the analysis based on the physical phase shift of pion-nucleon scattering in the channel. This finding suggests that the repulsive force between hadrons is interaction-channel dependent and is hence unlikely to be captured by a single phenomenological parameter. The S-matrix approach employed here can be used, however, to provide useful estimates of the magnitude of the effective eigenvolume.

    Comments:
    6 pages, 2 figures, submitted to phys. rev. c
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1703.00306 [pdf]
    PRC(2017)·39 citations

Affiliations

first authorsco-authorsvia INSPIRE