Observation of τ Lepton Pair Production in Ultraperipheral Pb-Pb Collisions at √s_NN=5.02 TeV

Authors

A. Tumasyan, CMS Collaboration

Date of this Version

10-12-2023

Citation

PHYSICAL REVIEW LETTERS 131, 151803 (2023). DOI: 10.1103/PhysRevLett.131.151803

Comments

Used by permission.

Abstract

We present an observation of photon-photon production of τ lepton pairs in ultraperipheral lead-lead collisions. The measurement is based on a data sample with an integrated luminosity of 404 μb⁻¹ collected by the CMS experiment at a center-of-mass energy per nucleon pair of √s_NN = 5.02 TeV. The γγ → τ⁺τ⁻ process is observed for τ⁺τ⁻ events with a muon and three charged hadrons in the final state. The measured fiducial cross section is σ(γγ → τ⁺τ^-) = 4.8 ± 0.6(stat) ± 0.5(syst) μb, where the second (third) term corresponds to the statistical (systematic) uncertainty in σ(γγ → τ⁺τ⁻) in agreement with leading-order QED predictions. Using σ(γγ → τ⁺τ⁻), we estimate a model-dependent value of the anomalous magnetic moment of the τ lepton of a_τ = 0.001 ^+0.055_−0.089 .