2022/05/11 by A. Jofrehei, Jofrehei, Arash
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.2205.05312
openalex publication_date 2022/05/11 · openalex created_date 2022/05/22 · openalex updated_date 2026/07/28
The first observation of τ lepton pair production in ultraperipheral nucleus-nucleus collisions, a pure quantum electrodynamics (QED) process, is presented. The measurement is based on a data sample collected by the CMS experiment at a per nucleon center-of-mass energy of 5.02~TeV, and corresponding to an integrated luminosity of 404~μb-1. The γγ→τ+τ- production is observed with a statistical significance of at least five standard deviations for τ+τ- events with a muon and three charged hadrons in the final state. The cross section is measured in a fiducial phase space region, and is found to be σ(γγ→τ+τ-) = 4.8± 0.6 (stat)± 0.5 (syst)~μb, in agreement with leading-order QED predictions. The measurement, based on a small fraction of the expected integrated luminosity of the LHC nuclear program, establishes the potential for a substantially more precise determination of the anomalous magnetic moment of the τ lepton, which is currently poorly constrained.