Charm and beauty isolation from heavy flavor decay electrons in p+p and Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV at LHC

Abstract

We present an analysis on the heavy flavor hadron decay electrons with charm and beauty contributions decomposed via a data driven method in Pb+Pb collisions at √ NN = 5.02 TeV at LHC. The transverse momentum T spectra, nuclear modification factor AA and azimuthal anisotropic flow 2 distributions of electrons from charm and beauty decays are obtained. We find that the electron AA from charm ( c→e AA ) and beauty ( b→e AA ) decays are suppressed at T > 2.0 and T > 3.0 GeV/ in Pb+Pb collisions, respectively, which indicates that charm and beauty interact with and lose their energy in the hot-dense medium. A less suppression of electron AA from beauty decays than that from charm decays at 2.0 < T < 8.0 GeV/ is observed, which is consistent with the mass-dependent partonic energy loss scenario. A non-zero electron 2 from beauty decays ( b→e 2 ) is observed and in good agreement with ALICE measurement. At low T region from 1.0 to 3.0 GeV/ , a discrepancy between RHIC and LHC results is observed with 68% confidence level, which suggests different degree of thermalization of beauty quark under different temperatures of the medium. At 3.0 GeV/ < T < 7.0 GeV/ , b→e 2 deviates from a number-of-constituent-quark (NCQ) scaling hypothesis, which favors that beauty quark is unlikely thermalized in heavy-ion collisions at LHC energy.