BSM physics using photon-photon fusion processes in UPC in Pb+Pb collisions with the ATLAS detector

TL;DR

This paper discusses searches for physics beyond the Standard Model through photon-photon processes in ultra-peripheral Pb+Pb collisions at the LHC, focusing on tau lepton properties and light-by-light scattering.

Contribution

It presents new measurements constraining tau anomalous magnetic moments and investigates light-by-light scattering for signs of new particles like axion-like particles.

Findings

Stringent limits on tau g-2 from ATLAS data

High-statistics light-by-light scattering measurements

Potential to explore new physics beyond the Standard Model

Abstract

Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons, leading to multiple photon-induced processes. This proceeding presents searches for physics beyond the Standard Model enabled by photon-photon processes in both di-tau and diphoton final states. The tau-pair production measurements can constrain the tau lepton's anomalous magnetic dipole moment (g-2), and a recent ATLAS measurement using muonic decays of tau leptons in association with electrons and tracks provides one of the most stringent limits available to date. Similarly, light-by-light scattering proceeds via loop diagrams, which can contain particles not yet directly observed. Thus, high statistics measurements of light-by-light scattering provide a precise and unique opportunity to investigate extensions of the Standard Model, such as the presence of axion-like particles.