Acoplanarity of QED pairs accompanied by nuclear dissociation in ultra-peripheral heavy ion collisions

TL;DR

This study examines how nuclear dissociation influences the acoplanarity of dilepton pairs produced electromagnetically in ultra-peripheral heavy ion collisions, highlighting impact-parameter dependence and potential for centrality determination.

Contribution

It introduces a method to estimate nuclear dissociation probabilities for different neutron emissions and analyzes their effect on dilepton acoplanarity within a QED framework.

Findings

Significant impact-parameter dependence of dilepton acoplanarity.

Nuclear dissociation probability varies with neutron multiplicity.

Impact-parameter dependence is key to understanding broadening effects.

Abstract

This paper investigates the transverse momentum broadening effect for electromagnetic production of dileptons in ultra-peripheral heavy ion collisions accompanied by nuclear dissociation. The electromagnetic dissociation probability of nuclei for different neutron multiplicities is estimated, which could serve as a centrality definition (i.e. impact parameter estimate) in ultra-peripheral collisions. In the framework of lowest-order QED, the acoplanarity of dilepton pairs is calculated for different neutron emission scenarios in ultra-peripheral collisions, indicating significant impact-parameter dependence. The verification of impact-parameter dependence is crucially important to understand the broadening effect observed in hadronic heavy-ion collisions.