Charm and beauty isolation from heavy flavor decay electrons in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV at RHIC

Abstract

We present a study of charm and beauty isolation based on a data-driven method with recent measurements on heavy flavor hadrons and their decay electrons in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV at RHIC. The individual electron $p_{\mathrm{T}}$ spectra, $R_{\mathrm{AA}}$ and $v_2$ distributions from charmed and beauty hadron decays are obtained. We find that the electron $R_{\mathrm{AA}}$ from beauty hadron decays ($R_{\mathrm{AA}}^{\mathrm{b}\to \mathrm{e}}$) is suppressed in minimum bias Au+Au collisions but less suppressed compared with that from charmed hadron decays at $p_{\mathrm{T}}$ $>$ 3.5 GeV/$c$, which indicates that beauty quark interacts with the hot-dense medium with depositing its energy and is consistent with the mass-dependent energy loss scenario. For the first time, the non-zero electron $v_2$ from beauty hadron decays ($v_2^{\mathrm{b}\to \mathrm{e}}$) at $p_{\mathrm{T}}$ $>$ 3.0 GeV/$c$ is observed and shows smaller elliptic flow compared with that from charmed hadron decays at $p_{\mathrm{T}}$ $<$ 4.0 GeV/$c$. At 2.5 GeV/$c$ $<$ $p_{\mathrm{T}}$ $<$ 4.5 GeV/$c$, $v_2^{\mathrm{b}\to \mathrm{e}}$ is smaller than a number-of-constituent-quark (NCQ) scaling hypothesis. This suggests that beauty quark is unlikely thermalized and too heavy to be moved in a partonic collectivity in heavy-ion collisions at the RHIC energy.

6 pages, 4 figures