Impact of Glasma on heavy quark observables in nucleus-nucleus collisions at LHC

In the pre-thermal equilibrium stage of relativistic heavy-ion collisions, a strong quasi-classical transverse gluon field emerges at about tau(0) similar or equal to 0.1 fm/c and evolves together with their longitudinal counterparts according to the classical Yang-Mills (CYM) equations. Recently it has been shown that these fields induce a diffusion of charm quarks in momentum space resulting in a tilt of their spectrum without a significant drag. We find that in nucleus-nucleus collisions at LHC such a novel dynamics of charm quarks leads to an initial enhancement of the nuclear modification factor (R-AA) at p(T) larger than 2 GeV/c contrary to the standard lore. Moreover, the same dynamics leads to a larger final elliptic flow (v(2)) inducing a relation between R-AA and v(2) that is quite close to the experimental measurements. Our study also shows that such an initial pre-thermal stage is unlikely to be described in terms of a standard drag and diffusion dynamics, because even if one tune such coefficients to reproduce the same R-AA(P-T) this would imply a significantly smaller v(2). (C) 2019 The Authors. Published by Elsevier B.V.