Diffusion of charm and beauty in the Glasma

Abstract

Relativistic nuclear collisions offer a unique way to study strong interactions at very high energy. The collision process can be described within the gluon saturation framework as the interaction of two colored glasses, and because of this interaction strong longitudinal gluon fields, namely the Glasma, are produced immediately after the collision. Besides, heavy quarks are also produced in the very early stage and because of their large mass and small concentration, their motion does not affect the evolution of the Glasma, thus behaving as ideal probes of the Glasma itself. We study the evolution of the heavy quarks in the Glasma allegedly produced in high energy p-Pb collisions by solving consistently the equations of motion of the quarks in the evolving Glasma fields. We find that this motion can be understood in terms of diffusion in momentum space, similarly to the random motion of a heavy probe in a hot thermalized medium. We show how the diffusion of heavy probes affects the nuclear modification factor of D and B mesons in p-Pb collisions. *

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

“…Therefore, we find a significant enhancement of the R AA (p T ) at intermediate p T associated to a depletion at low momenta. Such a dynamics is the result of the diffusion of the heavy quarks in the evolving gluon fields as already studied in the context of pA collisions in [28]. Certainly in AA collisions we have never observed such a behavior of R AA (p T ) because the initial stage is followed by a long phase of in-medium charm quark scattering.…”

“…As in [19,28] we deal with the SU(2) gauge theory for simplicity, we thus have f abc = ε abc with ε 123 = +1. The CYM equations are…”

“…According to the the color glass condensate (CGC) effective theory [23][24][25][26], the dense gluon system produced by the interaction of two colored glasses immediately after the collision can be described in terms of classical longitudinal fields named the Glasma, whose evolution in the early stage can be described by means of the classical Yang-Mills (CYM) equations. Recent works have investigated the impact of the propagation of charm and beauty in the Glasma [19,[27][28][29] with particular reference to the diffusion in momentum space. Here we study for the first time how the interaction of the heavy quarks with the Glasma affects the dynamics of HQs in AA collisions; we achieve this by implementing a simulation of the HQs dynamics including both the glasma and the QGP stages.…”

Probing the gluon plasma with charm balance functions

“…We also note that an out-of-equilibrium calculation, using the Glasma formalism, was presented in Ref. [43]. At the qualitative level, we predict that one should observe something very different from what was measured for light quarks, cf.…”

“…The production rate will be scaled up to account for the nuclear overlap geometry. We also mention that phenomeno-logical studies of charm-charm correlation functions have previously been done for flow [40], thermalization [41,42], jet quenching [26], and even for the effects of pre-equilibrium physics [43]. The idea to study charm-charm correlation functions (and even balance functions) is therefore not new and even the idea to use it as a probe of early-time physics can be found in some of these papers.…”