# Testing Charm Quark Equilibration in Ultra-High Energy Heavy Ion Collisions with Fluctuations

## TL;DR

This paper investigates Charm quark equilibration in ultra-high energy heavy ion collisions by analyzing lattice QCD susceptibilities and experimental fluctuations to determine the equilibration temperature and volume.

## Contribution

It introduces a method combining lattice QCD susceptibilities with experimental data to infer Charm quark equilibration parameters in the QGP.

## Key findings

- Lattice QCD provides higher order susceptibilities of Charm quarks.
- A new approach to infer Charm quark equilibration temperature and volume.
- First perturbative calculations of Charm susceptibilities and their ratios.

## Abstract

Recent lattice QCD data on higher order susceptibilities of Charm quarks provide the opportunity to explore Charm quark equilibration in the early quark gluon plasma (QGP) phase. Here, we propose to use the lattice data on second and fourth order net Charm susceptibilities to infer the Charm quark equilibration temperature and the corresponding volume, in the early QGP stage, via a combined analysis of experimentally measured multiplicity fluctuations. Furthermore, the first perturbative results for the second and fourth order Charm quark susceptibilities and their ratio are presented.