Search for stealth SYY top squark decays with an automated ABCD method using a double disco neural network in proton-proton collisions at √s = 13 tev with the CMS experiment

In this thesis, a search is presented for new physics beyond the standard model which includes a version of Supersymmetry (SUSY) characterized by Stealth SYY¯ SUSY. This search considers events with two top quarks, no extra transverse momentum, and many light flavor jets as pair-produced top squark decays. The Run2 data used were collected with the CMS detector at the LHC from 2016 to 2018, and correspond to a total integrated luminosity of 138 fb−1. An automated ABCD method using a Double DisCo Neural Network is implemented to estimate the main irreducible background (tt¯+jets) in data. The analysis considers the three orthogonal decay channels: fully-hadronic, semi-leptonic and fully leptonic and the results of these channels are combined for best signal sensitivity.