# Role of the spectator system in electromagnetic effects

## TL;DR

This paper investigates how electromagnetic effects and spectator system dynamics influence charged pion spectra and the space-time evolution in ultrarelativistic heavy ion collisions, combining experimental data, simulations, and theoretical models.

## Contribution

It provides a comprehensive analysis of electromagnetic phenomena and spectator fragmentation effects in peripheral Pb+Pb collisions at CERN SPS energies, integrating experimental, simulation, and theoretical approaches.

## Key findings

- Electromagnetic effects significantly influence charged pion spectra.
- Spectator system properties impact the space-time evolution of collisions.
- The study combines experimental data with advanced theoretical models.

## Abstract

The electromagnetic effects on charged pion ($\pi^+,\pi^-$) spectra provide new, independent information on the space-time evolution of the ultrarelativistic heavy ion collision. The spectator life time and its excitation energy may also be of importance for the understanding of the space-time evolution of the participant zone. This paper gives an overview of our coordinated effort to understand the interplay between electromagnetic phenomena and processes related to the fragmentation of the spectator system at forward rapidity in peripheral $Pb$+$Pb$ collisions at top CERN SPS energies. Our study includes on one hand the experimental analysis of electromagnetic effects and corresponding phenomenological Monte Carlo simulations, and on the other hand dedicated theoretical calculations based on the Abrasion-Ablation model ABRABLA and the 4D Langevin approach.