A search for natural supersymmetry via electroweak processes with Higgs and Z bosons in the final state

Abstract

OF THE DISSERTATION A Search for Natural Supersymmetry via Electroweak Processes with Higgs and Z Bosons in the Final State By PATRICK W. ZYWICKI Dissertation Director: Prof. Sunil Somalwar We present the individual and combined results of several analyses that search for the next-tolightest supersymmetric particle (NLSP) in the context of the Natural Higgsino NLSP model. The model posits that the NLSP is in a pure Higgsino energy eigenstate, and upon production mediated by electroweak processes, decays to either a Higgs or Z boson and the lightest supersymmetric particle (LSP), which is in a pure Bino energy eigenstate. The Higgs and Z bosons then decay in the Standard Model (SM) fashion, leading to a number of possible final states, all of which include missing transverse energy (MET) coming from the LSP. Six independent analyses search for the existence of the Higgsino-like NLSP by examining events that have the signature of a particular final state of the model. In addition to MET, these unique final states include multileptons, four b-jets, two photons and two b-jets, two photons and a lepton, two b-jets and two leptons, and two light-flavored jets and two leptons. The data used was collected during the 2012 run of the CMS experiment at √ s = 8 TeV and Lint = 19.5fb −1. No physics beyond the Standard Model was discovered. We therefore set limits on the mass of the Higgsino and the branching fraction of the Higgsino decays to Higgs and Z bosons.