Estimation of the SM background for search of electroweakinos with an isolated lepton, jets and missing transverse energy at center-of-mass energy of 13 TeV using the ATLAS detector

Supersymmetric extension of the Standard Model of particle physics addresses most of the SM open questions. One of the predictions of the model is that the lightest supersymmetric particle (LSP) must have mass of the O(1 TeV) (electroweak scale) which is within the reach of the current accelerators. The present work is part of a larger analysis which aims to search for the pair-produced chargino and neutralino, or two charginos using the final state of single lepton coming from W boson decay, light jets produced from W/Z decays and, the missing transverse energy expected due to escape of the LSP. First part of the analysis quantifies the kinematic agreement among the region definitions used estimate the SM background yields for Monte Carlo simulated samples containing electroweak decay of top quark. The yield variation (interpreted as systematic error) obtained during the extrapolation of the background to the region of signal events is less than 10%, thus providing a strong argument in the favor of the employed kinematic selection conditions. The second part of the analysis uses the associated production of two bosons to evaluate the impact of uncertainties arising from the non-perturbative dynamics of the model used to simulate the diboson decay channels. The results of our analysis show that the impact of mismodelling due to theoretical uncertainties are well within the acceptable range of 40% and thus, the estimated background along with the uncertainties can be taken as input for the likelihood fit and the subsequent steps of the analysis.