Fake lepton studies in a search for heavy scalar in dilepton + jets final states with ATLAS detector

Abstract

The estimation of fake lepton background is presented for the physics beyond the Standard Model search in the final state with a pair of different flavour opposite-sign leptons, eµ, accompanied by at least two jets. The search uses the LHC full Run 2 data recorded at a center-of-mass energy of 13 TeV collected with the ATLAS detector, with the corresponding luminosity of 139 fb−1 . The search extends the Standard Model by introducing the heavy scalar, H, and the additional Higgs-like scalar, S. One of the challenges in most physics analysis is to estimate background processes that can enter the signal region and be misidentified as the signal. This thesis focuses on the W+jets background which enters the signal region. From the W+jets background process, there is one real lepton from W and one fake which originates from the jet misidentified as a lepton. The Monte Carlo simulation cannot be trusted for the estimation of W+jets background as the rate of misidentification might not be well modelled. Hence one has to develop the data-driven techniques for the W+jets estimation. In the H → Sh → e ±µ ∓+jets analysis, the fake factor method is used for fake estimation.