Anisotropic fluctuations of angular momentum of heavy quarks in the Glasma

TL;DR

This paper investigates how anisotropic Glasma fields influence the early-stage angular momentum fluctuations of heavy quarks in high-energy nuclear collisions, revealing anisotropic behavior mainly in orbital angular momentum.

Contribution

It introduces a kinetic framework for analyzing angular momentum fluctuations of heavy quarks in Glasma fields, highlighting anisotropic fluctuations in the early collision stage.

Findings

Angular momentum fluctuations are anisotropic due to background field anisotropy.

Orbital angular momentum exhibits substantial diffusion and fluctuations.

Spin fluctuations remain negligible compared to orbital angular momentum.

Abstract

We study the evolution of the angular momentum of the heavy quarks in the very early stage of high energy nuclear collisions, in which the background is made of evolving Glasma fields. Given the novelty of the problem, we limit ourselves to the use of toy heavy quarks with a large, unphysical mass, in order to implement the kinetic equations for the angular momentum in the non-relativistic limit. We find that as a consequence of the anisotropy of the background fields, angular momentum fluctuations are also anisotropic: we understand this in simple terms relating the fluctuations of the angular momentum, $L$, to those of linear momentum. While orbital angular momentum diffuses and develops substantial fluctuations and anisotropies, the spin does not. Hence, we can identify the fluctuations of $L$ with those of the total angular momentum $J=L + S$. Therefore, our study suggests that the total angular momentum of the heavy quarks in the early stage of high energy nuclear collisions will present anisotropic fluctuations.