Charm balance function in relativistic heavy-ion collisions

TL;DR

This paper models the evolution of charm quark pairs in heavy-ion collisions using hydrodynamics and Langevin dynamics, predicting how charm balance functions reflect thermalization and rescattering effects.

Contribution

It introduces a comprehensive model combining hydrodynamics and Langevin equations to predict charm balance functions in heavy-ion collisions.

Findings

Reproduces azimuthal collimation due to transverse flow.

Shows charm quark thermalization in dense matter.

Predicts sensitivity of rapidity and azimuthal balance functions to rescattering.

Abstract

We calculate the balance function for charm in relativistic heavy-ion collisions. The distribution of pairs of charm-anticharm quarks produced in hard processes in the early stages of the nucleus-nucleus collision evolves in the dense fireball formed in the collision. The evolution of the dense matter is described using a relativistic viscous hydrodynamic model and the quark diffusion with a Langevin equation. The evolution of the charm quark balance function from the formation of the charm-anticharm pair up to the freeze-out traces the partial thermalization of the heavy quarks in the dense matter. For the balance function in azimuthal angle we reproduce the collimation effect due to the transverse flow. The evolution in rapidity shows the thermalization of the longitudinal velocity of the quark in the fluid. We provide predictions for the one and two-dimensional balance functions for $D^0$-$\bar{D^0}$ mesons produced in ultarelativistic Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. The shape of the charm balance function in relative rapidity is sensitive to the rescattering of heavy quarks in the early stages of the collision, while the shape of the balance function in azimuthal angle is sensitive to the rescattering in the latter stages.