Heavy-quark production and elliptic flow in Au + Au collisions atsNN=62.4GeV

Abstract

We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity (|y|< 0.35) in Au+Au collisions at sNN−−−−√=62.4 GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range 1<peT<5 GeV/c. The invariant yield per binary collision is slightly enhanced above the p+p reference in Au+Au 0%–20%, 20%–40%, and 40%–60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The v2 of electrons from heavy-flavor decays is nonzero when averaged between 1.3<peT<2.5 GeV/c for 0%–40% centrality collisions at sNN−−−−√=62.4 GeV. For 20%–40% centrality collisions, the v2 at sNN−−−−√=62.4 GeV is smaller than that for heavy-flavor decays at sNN−−−−√=200 GeV. The v2 of the electrons from heavy-flavor decay at the lower beam energy is also smaller than v2 for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at sNN−−−−√=200 GeV.