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

Summary, in English

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 final 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 differences 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 flavour universality in W-boson decays. © The Author(s) 2025.

• Author: G. Aad; T.P.A. Åkesson; K.S.V. Astrand; C. Doglioni; P.A. Ekman; V. Hedberg; H. Herde; B. Konya; E. Lytken; R. Poettgen; O. Smirnova; E.J. Wallin; L. Zwalinski
• Department/s: Particle and nuclear physics; eSSENCE: The e-Science Collaboration; Department of Physics
• Publishing year: 2025
• Language: English
• Publication/Series: Journal of High Energy Physics
• Volume: 2025
• Issue: 5
• Links: http://dx.doi.org/10.1007/JHEP05(2025)038
• Document type: Journal article
• Publisher: Springer
• Topic: Subatomic Physics
• Keywords: Flavour Physics; Hadron-Hadron Scattering; Tau Physics
• Status: Published
• ISBN/ISSN/Other: ISSN: 1029-8479