Diffusion of heavy quarks in the early stage of high-energy nuclear collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

TL;DR

This paper investigates how heavy quarks like charm and beauty diffuse in the early Glasma stage of high-energy nuclear collisions, revealing their significant impact on observed suppression patterns and emphasizing the importance of early-stage dynamics.

Contribution

It introduces a model that includes longitudinal expansion and gluon radiation effects in heavy quark diffusion during the Glasma phase, providing new insights into initial state effects.

Findings

Heavy quarks diffuse rapidly in early Glasma fields.

Results align qualitatively with experimental suppression data.

Early Glasma phase significantly influences heavy quark spectra.

Abstract

We study the diffusion of charm and beauty in the early stage of high energy nuclear collisions at RHIC and LHC energies, considering the interaction of these heavy quarks with the evolving Glasma by means of the Wong equations. In comparison with previous works, we add the longitudinal expansion as well as we estimate the effect of energy loss due to gluon radiation. We find that heavy quarks diffuse in the strong transverse color fields in the very early stage (0.2-0.3 fm/c) and this leads to a suppression at low $p_T$ and enhancement at intermediate low $p_T$. The shape of the observed nuclear suppression factor obtained within our calculations is in qualitative agreement with the experimental results of the same quantity for $D-$mesons in proton-nucleus collisions. We compute the nuclear suppression factor in nucleus-nucleus collisions as well, for both charm and beauty, finding a substantial impact of the evolving Glasma phase on these, suggesting that initialization of heavy quarks spectra in the quark-gluon plasma phase should not neglect the early evolution in the strong gluon fields.