UBC Faculty Research and Publications

Test of lepton favour universality in W-boson decays into electrons and τ -leptons using pp collisions at √s = 13 TeV with the ATLAS detector ATLAS Collaboration

Abstract

A measurement of the ratio of the branching fractions, Rτ /e = B(W → τν)/B(W → eν), is performed using a sample of W bosons originating from top-quark decays to fnal states containing τ -leptons or electrons. This measurement uses pp collisions at √s = 13 TeV, collected by the ATLAS experiment at the Large Hadron Collider during Run 2, corresponding to an integrated luminosity of 140 fb−1. The W → τντ (with τ → eνeντ) and W → eνe decays are distinguished using the diferences in the impact parameter distributions and transverse momentum spectra of the electrons. The measured ratio of branching fractions Rτ /e = 0.975 ± 0.012 (stat.) ± 0.020 (syst.), is consistent with the Standard Model assumption of lepton favour universality in W-boson decays.

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Attribution 4.0 International (CC BY 4.0)