Large Baryon Densities Achievable in High Energy Heavy Ion Collisions Outside the Central Rapidity Region

TL;DR

This paper calculates high baryon densities in receding nuclear fireballs during high energy heavy ion collisions, providing initial conditions for hydrodynamic models and insights into the equation of state at extreme densities.

Contribution

It introduces a method to estimate baryon and energy densities in receding fireballs outside the central rapidity region using the color glass condensate model.

Findings

Baryon densities exceed ten times normal nuclear matter.

High energy density matter is produced in receding fireballs.

Results serve as initial conditions for hydrodynamic evolution.

Abstract

Nuclei are nearly transparent to each other when they collide at high energy, but the collisions do produce high energy density matter in the central rapidity region where most experimental measurements are made. What happens to the receding nuclear fireballs? We calculate the energy loss of the nuclei using the color glass condensate model. We then use a simple space-time picture of the collision to calculate the baryon and energy densities of the receding fireballs. For central collisions of large nuclei at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider we find baryon densities more than ten times that of normal nuclear matter. These results provide initial conditions for subsequent hydrodynamic evolution and could test the equation of state at very high baryon densities.