Investigating QCD Dynamical Entropy in high-energy nuclear collisions

TL;DR

This paper extends the concept of QCD dynamical entropy to heavy ion collisions, using unintegrated gluon distributions to estimate initial entropy density and analyzing its dependence on nuclear size.

Contribution

It introduces a method to calculate QCD dynamical entropy in heavy ion systems using nuclear gluon distributions and demonstrates its independence from nucleus size.

Findings

Dynamical entropy density can be estimated from unintegrated gluon distributions.

Normalization and geometric scaling make entropy nearly nucleus-size independent.

Results provide initial entropy density estimates in ultra-relativistic collisions.

Abstract

In this work, the concept of QCD dynamical entropy is extended to heavy ion systems. This notion of entropy can be understood as a relative entropy and can also be used to estimate the initial entropy density in ultra-relativistic heavy ion collisions. The key quantity used to calculate this entropy is the nuclear unintegrated gluon distribution (nUGD), which provides a transverse momentum probability density. In the numerical analysis, both the geometric scaling phenomenon and the Glauber-Gribov approach have been used to evaluate realistic models for the nUGD. It is shown that the normalization procedure and the geometric scaling property make the dynamical entropy almost independent of the nucleus mass number $A$. Results are presented for the dynamical entropy density, $dS_D/dy$, in terms of the rapidity.