Department of Physics and Astronomy: Publications and Other Research


Date of this Version



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


Used by permission.


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 √sNN = 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 aτ = 0.001 +0.055−0.089 .

Included in

Physics Commons