Charm and beauty isolation from heavy flavor decay electrons in p+p and Pb+Pb collisions at sNN = 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 p+p and Pb+Pb collisions at sNN = 5.02 TeV at LHC. The transverse momentum pT spectra, nuclear modification factor RAA and azimuthal anisotropic flow v2 distributions of electrons from charm and beauty decays are obtained. We find that the electron RAA from charm (RAAc→e) and beauty (RAAb→e) decays are suppressed at pT>2.0 GeV/c in Pb+Pb collisions, which indicates that charm and beauty interact with and lose their energy in the hot-dense medium. A less suppression of RAAb→e than RAAc→e at 2.0<pT<8.0 GeV/c is observed, which is consistent with the mass-dependent partonic energy loss scenario. A non-zero electron v2 from beauty decays (v2b→e) is observed and in good agreement with ALICE measurement. At low pT from 1.0 to 3.0 GeV/c, a discrepancy between RHIC and LHC results is observed with an 85% confidence level, which might be a possible hint of an energy-dependent behavior of beauty quarks reacting with the medium created in heavy-ion collisions. At 3.0<pT<7.0 GeV/c, v2b→e 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.

Keywords

• Quark-gluon plasma
• Charm
• Beauty
• Semileptonic decay
• Nuclear modification factor
• Elliptic flow