Do electromagnetic effects survive in the production of lepton pairs in nucleus-nucleus collisions ?

TL;DR

This paper investigates electromagnetic effects in lepton pair production during nucleus-nucleus collisions, emphasizing photoproduction mechanisms and explaining recent experimental results from ALICE and STAR collaborations.

Contribution

It provides a detailed analysis of electromagnetic effects in semi-central and peripheral heavy-ion collisions, highlighting their significance in low transverse momentum lepton pair production.

Findings

Electromagnetic effects are significant in low transverse momentum $J/\psi$ production.

Photoproduction mechanisms explain recent experimental observations.

Electromagnetic effects are relevant in semi-central collision processes.

Abstract

We discuss production of $J/\psi$ and $e^+ e^-$ pairs in semicentral and peripheral collisions of heavy ions at high energies. We focus on photoproduction mechanism. We present explanation of results of the ALICE collaboration for low transverse momentum production of $J/\psi$ as well as results obtained by the STAR collaboration for $e^+ e^-$ production, also at low transverse momenta. We conclude that such effects are important also in this new corner (semi-central processes) of the phase space.