Abstract
We study the production of heavy quarks, charm at BNL-RHIC (root s = 200 GeV/nucleon) and CERN-LHC (root s = 5.5 TeV/nucleon) and bottom at CERN-LHC, from heavy ions colliding at relativistic energies. We consider initial fusion of gluons (and quark-anti-quark annihilation), pre-thermal parton interactions and interactions in a thermalized quark-gluon plasma. We also consider free-streaming partons as another extreme and compare the results with those from a thermalized plasma of partons. The pre-thermal contribution is calculated by considering the interaction among partons having large transverse momenta (jet-partons) after the initial interaction and from the passage of these partons through a thermalized quark-gluon plasma. Charm production from pre-thermal processes is found to be comparable to that from prompt (initial) interactions at LHC. It is suggested that this may have important implications for the study of the nuclear modification factor, R-AA, as well as for the back-to-back correlation of heavy quarks and the production of dileptons having a large mass.