Probing Hot and Dense Matter with Charm and Bottom Measurements with PHENIX VTX Tracker

摘要

We present the first measurements of the nuclear modification factor (RAA) for flavor-separated b, c-quark electrons in Au+Au collisions at √s_(NN) = 200 GeV. The newly installed Silicon Vertex Tracker is used to measure the distance of closest approach distributions of electrons at midrapidity (|η|< 0.35) over the transverse momentum range 1 _T~e < 5 GeV/c. From this, the relative fraction of bottom (b) and charm (c) quarks is determined in both the p+p and Au+Au collision systems, which form the basis of the measured R_(AA). In p+p, we observe that a FONLL perturbative QCD calculation of b →e/(c →e+b →e) ratio is in good agreement with the data. In Au+Au, the data imply a large suppression of b→e or a large modification of B meson p_T distributions, which implies very interesting physics of B mesons in Au+Au collisions.