# Achieving high baryon densities in the fragmentation regions in heavy ion collisions at top RHIC energy

## TL;DR

This paper demonstrates that in high-energy heavy ion collisions at RHIC, the fragmentation regions can reach baryon densities approximately twenty times higher than normal nuclear matter, due to nuclear compression effects.

## Contribution

The study provides a calculation of net-baryon rapidity loss and nuclear excitation energy using the McLerran-Venugopalan model, revealing conditions for extremely high baryon densities in fragmentation regions.

## Key findings

- High baryon densities (~20 times nuclear density) are achievable in fragmentation regions.
- Nuclear compression during collisions significantly increases baryon density.
- Net-baryon rapidity loss and excitation energy are quantitatively estimated.

## Abstract

Heavy ion collisions at extremely high energy, such as the top energy at RHIC, exhibit the property of transparency where there is a clear separation between the almost net-baryon-free central rapidity region and the net-baryon-rich fragmentation region. We calculate the net-baryon rapidity loss and the nuclear excitation energy using the energy-momentum tensor obtained from the McLerran-Venugopalan model. Nuclear compression during the collision is further estimated using a simple space-time picture. The results show that extremely high baryon densities, about twenty times larger than the normal nuclear density, can be achieved in the fragmentation regions.