Exploring non-equilibrium quark-gluon plasma effects on charm transport coefficients

We investigate how the drag coefficient A and (q) over cap, the transverse momentum transfer by unit length, of charm quarks are modified if the quark-gluon plasma (QGP) is not in complete thermal equilibrium using the dynamical quasiparticle model (DQPM), which reproduces both, the equation-of-state of the QGP and the spatial diffusion coefficient of heavy quarks as predicted by lattice quantum chromodynamics calculations. We study three cases: (i) the QGP has an anisotropic momentum distribution of the partons, which leads to an anisotropic pressure; (ii) the QGP partons have higher or lower kinetic energies as compared to the thermal expectation value; and (iii) the QGP partons have larger or smaller pole masses of their spectral function as compared to the pole mass from the DQPM at the QGP temperature. In the last two cases we adjust the number density of partons to obtain the same energy density as in an equilibrated QGP. We find that each non-equilibrium scenario affects A and (q) over cap of charm quarks in a different way. The modifications in our scenarios are of the order 20-30% at temperatures relevant for heavy-ion reactions. These modifications have to be considered if one wants to determine these coefficients by comparing heavy-ion data with theoretical predictions from viscous hydrodynamics or Langevin equations.