Elliptic Flow of Heavy-Flavor Decay Electrons in Au+Au Collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 27 and 54.4 GeV at RHIC

Abstract

We report on new measurements of elliptic flow ($v_2$) of electrons from heavy-flavor hadron decays at mid-rapidity ($|y|<0.8$) in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons ($e^{\mathrm{HF}}$) in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 54.4 GeV exhibit a non-zero $v_2$ in the transverse momentum ($p_{\mathrm{T}}$) region of $p_{\mathrm{T}}<$ 2 GeV/$c$ with the magnitude comparable to that at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. The measured $e^{\mathrm{HF}}$ $v_2$ at 54.4 GeV is also consistent with the expectation of their parent charm hadron $v_2$ following number-of-constituent-quark scaling as other light and strange flavor hadrons at this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=54.4$ GeV. The measured $e^{\mathrm{HF}}$ $v_2$ in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 27 GeV is consistent with zero within large uncertainties. The energy dependence of $v_2$ for different flavor particles ($\pi ,\varphi ,D^0/e^{\mathrm{HF}}$) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.

12 pages, 7 figures, 1 table

References in corpus (20)

• PYTHIA 6.4 Physics and Manual
• Glauber Modeling in High Energy Nuclear Collisions
• Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR
• Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• Observation of $D^0$ meson nuclear modifications in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 200 GeV
• Charmonium properties in hot quenched lattice QCD
• Strange and Multi-strange Particle Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 62.4 GeV
• Centrality and transverse momentum dependence of $D^0$-meson production at mid-rapidity in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$
• Lattice QCD constraints on the heavy quark diffusion coefficient
• The STAR Vertex Position Detector
• High $p_T$ non-photonic electron production in $p$+$p$ collisions at $\sqrt{s}$ = 200 GeV
• Measurement of azimuthal anisotropy of muons from charm and bottom hadrons in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ATLAS detector
• Observation of $D_s^{\pm }/D^0$ enhancement in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 200 GeV
• Azimuthal anisotropy measurements of strange and multistrange hadrons in U+U collisions at $\sqrt{s_{NN}}=193$ GeV at the BNL Relativistic Heavy Ion Collider
• Calculating the initial energy density in heavy ion collisions by including the finite nuclear thickness
• Properties of the QGP created in heavy-ion collisions
• Modifications of Heavy-Flavor Spectra in $\sqrt{s_{\mathrm{NN}}}=62.4\mathrm{GeV}$ Au-Au Collisions
• Measurement of cold nuclear matter effects for inclusive $J/\psi$ in $p$+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 200 GeV
• Directed and elliptic flow of identified hadrons, high-$p_{\mathrm{T}}$ charged hadrons and light nuclei in Au+Au collisions at STAR
• Measurement of inclusive electrons from open heavy-flavor hadron decays in $p$+$p$ collisions at $\sqrt{s}=200$ GeV with the STAR detector

Cited by in corpus (2)

• Properties of the QCD Matter -- An Experimental Review of Selected Results from RHIC BES Program
• Elliptic anisotropy of open-charm hadrons from parton scatterings in p--Pb collisions at energies available at the CERN Large Hadron Collider