Hunting for New Physics with Improved Tests of Lepton Flavor Universality at High Luminosity Large Hadron Collider

One of the fundamental axioms of the Standard Model is Lepton Flavour Universality (LFU), meaning that the photon, W and Z bosons couple in exactly the same manner to the three lepton generations. To test this assumption, we measure the ratio of branching fractions of W-boson decays to τ and light leptons in tt¯ events with the ATLAS detector. This analysis predicts the sensitivity of this measurement at HL-LHC, which will conceivably allow for unprecedented precision to beyond the Standard Model physics. With halved theory systematics and low pT muon uncertainty and exclusion of Monte Carlo statistical uncertainties, a precision of 0.27% is obtainable.