Tests of the Quark-Gluon Plasma Coupling Strength at Early Times with Heavy Quarks

TL;DR

This study uses Monte Carlo Langevin simulations within hydrodynamic models to investigate how heavy quarks probe the early-time coupling strength of the quark-gluon plasma, revealing different sensitivities for charm and beauty quarks.

Contribution

It introduces a novel approach combining Langevin dynamics with hydrodynamics to analyze heavy quark interactions, highlighting their potential to map the plasma's temperature-dependent properties.

Findings

Charm quark R_{AA} is insensitive to early-time coupling.

Charm-anticharm azimuthal correlations are highly sensitive to early-time evolution.

Beauty quark observables show reversed sensitivity compared to charm.

Abstract

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 acheived. 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. Future measurements of heavy quarks have the potential to map out the temperature dependence of the shear viscosity to entropy density ratio ({\eta}/s).