Heavy-quark dynamics and hadronization in ultrarelativistic heavy-ion collisions: Collisional versus radiative energy loss

We study the dynamics of energy loss and flow of heavy quarks produced in ultrarelativistic heavy-ion collisions within the framework of a Langevin equation coupled to a ($2+1$)-dimensional viscous hydrodynamic model that simulates the spacetime evolution of the produced hot and dense QCD matter. The classical Langevin approach is improved such that, apart from quasielastic scatterings, radiative energy loss is incorporated by treating gluon radiation as an additional force term. The hadronization of emitted heavy quarks is simulated via a hybrid fragmentation plus recombination model. Our calculation shows significant contribution from gluon radiation to heavy quark energy loss at high energies, and we find the recombination mechanism is important for heavy flavor meson production at intermediate energies. We present numerical results for the nuclear modification and elliptic flow of $D$ mesons, which are consistent with measurements at both the CERN Large Hadron Collider (LHC) and the BNL Relativistic Heavy-Ion Collider (RHIC); predictions for $B$ mesons are also provided.