Monte Carlo event generation and model validation for lepton universality

<!--HTML-->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.<br><br>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.