Elliptic flow of electrons from heavy-flavor hadron decays in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200, 62.4, and 39 GeV

Abstract

We present measurements of elliptic flow ($v_2$) of electrons from the decays of heavy-flavor hadrons ($e_{HF}$) by the STAR experiment. For Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV we report $v_2$, for transverse momentum ($p_T$) between 0.2 and 7 GeV/c using three methods: the event plane method ($v_2${EP}), two-particle correlations ($v_2${2}), and four-particle correlations ($v_2${4}). For Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 62.4 and 39 GeV we report $v_2${2} for $p_T<2$ GeV/c. $v_2${2} and $v_2${4} are non-zero at low and intermediate $p_T$ at 200 GeV, and $v_2${2} is consistent with zero at low $p_T$ at other energies. The $v_2${2} at the two lower beam energies is systematically lower than at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV for $p_T<1$ GeV/c. This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to $\sqrt{s_{\mathrm{NN}}}=200$ GeV.

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