Testing Lepton Flavour Universality: A precise measurement of the ratio B(W→τν)/B(W→μν) with the ATLAS experiment

by Dr Christopher Young (Universität Freiburg)

Thursday 19 May 2022, 15:30 → 16:30 Europe/Berlin

CP-03-123 (TU Dortmund)

A fundamental property of the Standard Model is the universality of the couplings of the vector bosons to the different generations of leptons. This has been tested at various different experiments both at low mass scales and for on-shell bosons. At the Large Electron-Positron Collider the ratio of branching fractions between different generations for both the W and Z bosons were measured and a 2.7$\sigma$ discrepancy was observed in the ratio $\mathcal{B}(W^+\to\tau^+\nu_{\tau})/\mathcal{B}(W^+\to\mu^+\nu_{\mu})$, motivating its precise measurement at the LHC. A measurement of this ratio with the ATLAS experiment using W bosons from top-quark decays will be presented. This will be put into the broader context of measurements of lepton flavour universality at the LHC.

slides.pdf