Search for heavy FCNC quarks at 13 TeV pp collisions at the LHC

Abstract

In this thesis, we describe a search for heavy iso-singlet quarks that is foreseen by F. Gürsey, P. Sikivie, P. Ramond’s E6 grand unification model, through the pp → D ¯DX → HjZjX → 4j2`X flavor-changing neutral current decay channel. We use data from proton-proton collisions at 13TeV center-of-mass energy corresponding to 36.1fb−1 integrated luminosity that have been collected during 2015-2016 with the ATLAS Detector at the Large Hadron Collider. A cut-based selection algorithm is used to choose four jets and two opposite-sign same-flavor leptons, which are used to reconstruct the Z boson. No significant excess beyond SM predictions is observed. The lower limit of 1526.2+12.3 −14.6 GeV is set on the mass of E6 quark with 95% confidence-level by CLS method.