Examination whether heavy quarks carry information on the early-time coupling of the quark-gluon plasma

The redistribution in momentum space of heavy quarks via their interactions in the quark-gluon plasma is an excellent probe of the heavy quark coupling strength to the medium. We utilize a Monte Carlo Langevin calculation for tracking heavy quark-antiquark pairs embedded in a viscous hydrodynamic space-time evolution. We find that the nuclear modification factor (R-AA) for charm quarks is relatively insensitive to the coupling to the quark-gluon plasma at early times where the highest temperatures are achieved. In contrast the azimuthal angular correlation of charm and anticharm quarks is extremely sensitive to the early time evolution. For beauty quarks the situation is reversed in terms of sensitivity. This work identifies the kinematic distributions of the heavy quarks with the greatest sensitivity, and must be followed by tests of whether they survive hadronization, in particular if recombination is dominant.