From the Glasma to the QCD Phase Boundary

TL;DR

This paper discusses the properties of matter formed in high-energy nuclear collisions, emphasizing the invariance of the baryon chemical potential to temperature ratio across energies, and its implications for understanding the QCD phase boundary.

Contribution

It introduces a qualitative argument that the baryon chemical potential to temperature ratio remains approximately constant across energies at fixed rapidity, impacting QCD phase boundary studies.

Findings

The initial baryon chemical potential to temperature ratio is energy-independent at fixed rapidity.

Initial temperature and baryon number increase with collision energy.

The ratio's invariance suggests a consistent condition at the QCD phase boundary.

Abstract

In this paper, I qualitatively discuss the matter formed in the fragmentation region of nuclear collisions at the highest energies. I argue that although the initial temperature and baryon number density can become very large, the ratio of initial baryon chemical potential to initial temperature is approximately independent of energy, when measured at a fixed rapidity measured from the end of the fragmentation region. This quantity is argued to be roughly invariant under expansion, and therefore the value measured at decoupling should be approximately the same as the initial value and largely independent of energy. The values of the initial temperature and initial baryon number are energy dependent and become large as the center of mass collision energy increases.