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arXiv · 1404.2765

Examination of the directed flow puzzle in heavy-ion collisions

V. P. Konchakovski·W. Cassing·Yu. B. Ivanov·V. D. Toneev
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Abstract

Recent STAR data for the directed flow of protons, antiprotons, and charged pions obtained within the beam energy scan program are analyzed within the parton-hadron-string-dynamics (PHSD and HSD) transport models and a 3-fluid hydrodynamics (3FD) approach. Both versions of the kinetic approach, HSD and PHSD, are used to clarify the role of partonic degrees of freedom. The PHSD results, simulating a partonic phase and its coexistence with a hadronic one, are roughly consistent with data. The hydrodynamic results are obtained for two equations of state (EoS), a pure hadronic EoS and an EoS with a crossover type transition. The latter case is favored by the STAR experimental data. Special attention is paid to the description of antiproton directed flow based on the balance of $p\bar{p}$ annihilation and the inverse processes for $p\bar{p}$ pair creation from multimeson interactions. Generally, the semiqualitative agreement between the measured data and the model results supports the idea of a crossover type of quark-hadron transition that softens the nuclear EoS but shows no indication of a first-order phase transition.

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V. P. Konchakovski, W. Cassing, Yu. B. Ivanov, V. D. Toneev. 2014-07-14. Examination of the directed flow puzzle in heavy-ion collisions. https://doi.org/10.1103/physrevc.90.014903

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