Far-from-equilibrium heavy quark energy loss at strong coupling

TL;DR

This paper investigates heavy quark energy loss in far-from-equilibrium matter created in high-energy collisions, finding that equilibrium formulas surprisingly describe the energy loss well even before full thermalization.

Contribution

It demonstrates that equilibrium-based energy loss expressions are effective in modeling heavy quark dynamics in far-from-equilibrium conditions, bridging a gap in understanding early-stage quark-gluon plasma behavior.

Findings

Equilibrium expressions describe qualitative features of energy loss early on.

Quantitative agreement with viscous hydrodynamics at later times.

Discovery of a perpendicular force component on moving quarks in out-of-equilibrium matter.

Abstract

We study the energy loss of a heavy quark propagating through the matter produced in the collision of two sheets of energy [1]. Even though this matter is initially far-from-equilibrium we find that, when written in terms of the energy density, the equilibrium expression for heavy quark energy loss describes most qualitative features of our results well. At later times, once a plasma described by viscous hydrodynamics has formed, the equilibrium expression describes the heavy quark energy loss quantitatively. In addition to the drag force that makes it lose energy, a quark moving through the out-of-equilibrium matter feels a force perpendicular to its velocity.