# Core-Corona Separation in Ultra-Relativistic Heavy Ion Collisions

## TL;DR

This paper introduces a geometrical model to distinguish core and corona regions in ultra-relativistic heavy ion collisions, highlighting how peripheral collisions have a significant corona contribution affecting experimental results.

## Contribution

It provides a method to separate core and corona contributions in high energy nuclear collisions, improving interpretation of experimental data.

## Key findings

- Corona contribution is small in central collisions.
- Corona becomes more significant in peripheral collisions.
- Implications for RHIC and SPS collision results.

## Abstract

Simple geometrical considerations show that the collision zone in high energy nuclear collisions may be divided into a central part (``core''), with high energy densities, and a peripheral part (``corona''), with smaller energy densities, more like in pp or pA collisions. We present calculations which allow to separate these two contributions, and which show that the corona contribution is quite small (but not negligible) for central collisions, but gets increasingly important with decreasing centrality. We will discuss consequences concerning results obtained in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Super Proton Synchrotron (SPS).