Examination of the directed flow puzzle in heavy-ion collisions

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.

12 pages, 11 figures

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• The QCD equation of state with dynamical quarks
• The QCD transition temperature: results with physical masses in the continuum limit
• Parton transport and hadronization from the dynamical quasiparticle point of view
• From Kadanoff-Baym dynamics to off-shell parton transport
• Directed flow in ultrarelativistic heavy-ion collisions
• System-size independence of directed flow at the Relativistic Heavy-Ion Collider
• QCD thermodynamics and confinement from a dynamical quasiparticle point of view
• Onset of deconfinement in nucleus-nucleus collisions: Review for pedestrians and experts
• Directed and elliptic flow in heavy ion collisions from $E_{\mathrm{beam}}=90$ MeV/nucleon to $E_{c.m.}=200$ GeV/nucleon
• Lattice QCD Constraints on the Nuclear Equation of State
• Dilepton production in proton-proton and Pb+Pb collisions at sqrt(s_NN)=2.76 TeV
• Collective Flow in Heavy-Ion Collisions from AGS to SPS

Cited by in corpus (15)

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• Charge-dependent directed flow in asymmetric nuclear collisions
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• Directed flow of $\Lambda$ in high-energy heavy-ion collisions and $\Lambda$ potential in dense nuclear matter
• The first moment of azimuthal anisotropy in nuclear collisions from AGS to LHC energies
• Heavy quark scattering and quenching in a QCD medium at finite temperature and chemical potential
• Particle production and chemical freezeout from the hybrid UrQMD approach at NICA energies
• Global $\Lambda$ polarization in heavy-ion collisions at energies 2.4--7.7 GeV: Effect of Meson-Field Interaction
• Strangeness thermodynamic instabilities in hot and dense nuclear matter
• Directed flow in heavy-ion collisions at NICA: what is interesting to measure?
• Directed flow in heavy-ion collisions and its implications for astrophysics
• Anisotropic flow of charged and identified hadrons at FAIR energies and its dependence on the nuclear equation of state
• Directed flow of $\Lambda$, $\bar{\Lambda }$, $K^{\pm }$, $K_S^0$ and $\varphi$ mesons from Beam Energy Scan Au+Au collisions using the STAR experiment
• Directed flow of $\Lambda$ from heavy-ion collisions and hyperon puzzle of neutron stars