Photon-photon fusion and tau g-2 measurement in ATLAS

TL;DR

This paper reports on ATLAS measurements of photon-induced dilepton production, including tau pairs, to constrain the tau lepton's magnetic moment and study nuclear photon flux in heavy-ion collisions.

Contribution

It presents the first measurements of tau pair production via photon fusion at the LHC and sets new limits on the tau's anomalous magnetic dipole moment.

Findings

Constraints on tau lepton's magnetic dipole moment

Measurements of electron and muon pair production

Insights into nuclear photon flux dependence

Abstract

Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons. New measurements of exclusive dilepton production (electron, muon, and tau pairs) performed by the ATLAS experiment are discussed. We present the photon-induced production of tau pairs and constraints on the tau lepton's anomalous magnetic dipole moment. In addition, measurements of photon-induced electron and muon pair production are presented, which provide strong constraints on the nuclear photon flux and its dependence on the impact parameter and photon energy. Forward neutrons are utilised to provide an experimental handle on the impact parameter range sampled in the events.