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Torsten ÅKESSON

Torsten Åkesson

Professor

Torsten ÅKESSON

Observation of the γγ→ττ Process in Pb+Pb Collisions and Constraints on the τ-Lepton Anomalous Magnetic Moment with the ATLAS Detector

Author

  • G. Aad
  • T.P.A. Åkesson
  • E.E. Corrigan
  • C. Doglioni
  • P.A. Ekman
  • J. Geisen
  • V. Hedberg
  • G. Jarlskog
  • B. Konya
  • E. Lytken
  • K.H. Mankinen
  • J.U. Mjörnmark
  • G.A. Mullier
  • R. Poettgen
  • N.D. Simpson
  • E. Skorda
  • O. Smirnova
  • L. Zwalinski

Summary, in English

This Letter reports the observation of τ-lepton-pair production in ultraperipheral lead-lead collisions Pb+Pb→Pb(γγ→ττ)Pb and constraints on the τ-lepton anomalous magnetic moment a_{τ}. The dataset corresponds to an integrated luminosity of 1.44 nb^{-1} of LHC Pb+Pb collisions at sqrt[s_{NN}]=5.02 TeV recorded by the ATLAS experiment in 2018. Selected events contain one muon from a τ-lepton decay, an electron or charged-particle track(s) from the other τ-lepton decay, little additional central-detector activity, and no forward neutrons. The γγ→ττ process is observed in Pb+Pb collisions with a significance exceeding 5 standard deviations and a signal strength of μ_{ττ}=1.03_{-0.05}^{+0.06} assuming the standard model value for a_{τ}. To measure a_{τ}, a template fit to the muon transverse-momentum distribution from τ-lepton candidates is performed, using a dimuon (γγ→μμ) control sample to constrain systematic uncertainties. The observed 95% confidence-level interval for a_{τ} is -0.057

Department/s

  • Particle and nuclear physics
  • eSSENCE: The e-Science Collaboration

Publishing year

2023

Language

English

Publication/Series

Physical Review Letters

Volume

131

Issue

15

Document type

Journal article

Publisher

American Physical Society

Topic

  • Subatomic Physics

Keywords

  • Magnetic moments
  • Anomalous magnetic moments
  • ATLAS detectors
  • ATLAS experiment
  • Integrated luminosity
  • Lead collisions
  • Lepton pairs
  • Moment formula
  • Pair production
  • Particle tracks
  • Standard deviation
  • Charged particles

Status

Published

ISBN/ISSN/Other

  • ISSN: 1079-7114