We study charm production in ultrarelativistic heavy-ion collisions by using the parton-hadron-string dynamics (PHSD) transport approach. The initial charm quarks are produced by the pythia event generator tuned to fit the transverse-momentum spectrum and rapidity distribution of charm quarks from fixed-order next-to-leading logarithm calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the dynamical quasiparticle model (DQPM), which reproduces the lattice QCD equation of state in thermal equilibrium. The relevant cross sections are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and fragmentation. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective Lagrangian approach with heavy-quark spin symmetry. Finally, the nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$ of $D^0$ mesons from PHSD are compared with the experimental data from the STAR Collaboration for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200$ GeV. We find that in the PHSD the energy loss of $D$ mesons at high $p_T$ can be dominantly attributed to partonic scattering while the actual shape of $R_{AA}$ versus $p_T$ reflects the heavy-quark hadronization scenario, i.e., coalescence versus fragmentation. Also, the hadronic rescattering is important for the $R_{AA}$ at low $p_T$ and enhances the $D$-meson elliptic flow $v_2$.

• Received 11 March 2015
• Revised 20 May 2015

DOI:https://doi.org/10.1103/PhysRevC.92.014910