Searches for supersymmetry in the fully hadronic and Higgs to diphoton final states

Abstract

Searches for physics beyond the Standard Model (SM) are a main focus of the physics program at the Large Hadron Collider at CERN. I present in this thesis two searches for supersymmetry (SUSY), using data collected with the Compact Muon Solenoid detector. The first search is a broad range search for SUSY in the tails of the stransverse mass distribution MT2. Data collected in the year 2016 corresponding to an integrated luminosity of 35.9/fb are used to obtain data driven estimates of the \zinv, lost leptons and QCD multijet backgrounds. No sign of SUSY has been found. Upper limits on the production cross section of simplified models of SUSY are set. Gluino masses up to 2 TeV are excluded for a massless lightest supersymmetric particle (LSP). Squark masses up to 1 TeV(1.6 TeV) for one (four) light squark type(s) for a massless LSP are excluded. The second search explores strong and electroweak SUSY production through the final state of a Higgs boson decaying to a photon pair analyzing 77.5/fb of integrated luminosity collected in 2016 and 2017. The nonresonant diphoton background is estimated from fits to the data, while the resonant background from the SM Higgs boson production is estimated from simulation. To increase sensitivity with respect to the backgrounds, categories with leptons, jets, b-tagged jets, MT2 and the transverse momentum of the Higgs boson are employed. No significant excess over the SM prediction is found. Upper limits on the production cross section of simplified models of SUSY are set. Bottom squark masses up to 530 GeV are excluded for a massless LSP. For wino-like chargino-neutralino production masses below 220 GeV for a gravitino LSP mass of 1 GeV are excluded. For the higgsino-like chargino-neutralino production with 100% branching fraction LSP→Hgravitino masses up to 275 GeV and with 50% branching fraction to LSP→Hgravitino and LSP→Zgravitino masses up to 190 GeV are excluded for a gravitino mass of 1 GeV.