Baryon number fluctuations in chiral effective models and their phenomenological implications

Gábor András Almási, Bengt Friman, and Krzysztof Redlich
Phys. Rev. D 96, 014027 – Published 26 July 2017

Abstract

We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polyakov-loop extended quark-meson Lagrangian that includes the coupling of quarks to vector meson and temporal gauge fields. The functional renormalization group is employed to properly account for the O(4) criticality at the phase boundary. We focus on the properties and systematics of ratios of the net-baryon-number cumulants χBn, for 1n6, near the phase boundary. The results are presented in the context of the recent experimental data of the STAR Collaboration on fluctuations of the net proton number in heavy-ion collisions at RHIC. We show that the model results for the energy dependence of the cumulant ratios are in good overall agreement with the data, with one exception. At center-of-mass energies below 19.6 GeV, we find that the measured fourth-order cumulant deviates considerably from the model results, which incorporate the expected O(4) and Z(2) criticality. We assess the influence of model assumptions and in particular of repulsive vector-interactions, which are used to modify the location of the critical end point in the model, on the cumulants ratios. Finally, we discuss a possibility to test to what extent the fluctuations are affected by nonequilibrium dynamics by comparing certain ratios of cumulants.

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  • Received 21 March 2017

DOI:https://doi.org/10.1103/PhysRevD.96.014027

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Nuclear Physics

Authors & Affiliations

Gábor András Almási1,*, Bengt Friman1, and Krzysztof Redlich2,3

  • 1GSI Helmholtzzentrum für Schwerionenforschung, D-64291 Darmstadt, Germany
  • 2University of Wrocł aw, Institute of Theoretical Physics, PL 50-204 Wrocł aw, Poland
  • 3ExtreMe Matter Institute EMMI, GSI, D-64291 Darmstadt, Germany

  • *g.almasi@gsi.de

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Vol. 96, Iss. 1 — 1 July 2017

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