Monte Carlo event generation and model validation for lepton universality

The Standard Model predicts that the probability of electroweak decay of $W$ or $Z$ bosons to different flavour leptons should be the same. This is given by lepton universality, which gives the ratio of the decay of $W$ or $Z$ bosons to different flavours of leptons as unity. Previous Atlas measurements showed a consistent result in support of lepton universality. A recent measurement by LHCb hinted at a violation of lepton flavour universality, with a significance of 3.1 standard deviations. In this analysis, Physics Beyond the Standard Model (BSM) is studied to explain this potential violation.

This analysis probes the lepton universality by studying the BSM models such as a Charged Higgs boson, Leptoquarks, or the possible evidence of a $W$′ boson in the single lepton final state of the top-antitop pair production at the centre-of-mass energy of 13 TeV with the Atlas experiment. The events generated are folded to reco-level and statistical fit only limits are obtained on the BSM models.