UC Santa Barbara

This dissertation describes a search for R-parity violating supersymmetry, motivated by the stringent limits set on R-parity conserving models from Run I and Run II of the LHC. These limits have excluded gluno masses up to approximately 2 TeV in mass, which is the rough scale expected for supersymmetry to “naturally” solve the Hierarchy Problem. These constraints, however, can be evaded by considering R-parity violating models, in which the lightest supersymmetric particle can decay to Standard Model particles and does not produce a large missing transverse momentum signature.

To avoid conflicts with experimental measurements, such as proton decay, the framework of Minimal Flavor Violation is applied, resulting in the largest R-parity violating coupling being between a top, bottom, and strange quark. Therefore, this search uses the pair production of gluinos that decay via g̃ → t̅t̃ → t̅b̅s̅ as a benchmark model and generically looks for new physics with a signature of a single lepton, large jet and bottom quark jet multiplicities, and high sum of large-radius jet masses, without any requirement on the missing transverse momentum in an event.

The search is conducted with 35.9 fb⁻¹ of √s = 13 TeV proton-proton collisions collected by the CMS experiment in 2016. The background is estimated through a maximum-likelihood fit of the N_b distribution across bins of jet multiplicity and sum of large-radius jet masses. No evidence of new physics is observed, and limits on a simplified model, in which gluinos decay promptly via g̃ → t̅b̅s̅, are set, excluding gluino masses below 1610 GeV at the 95% confidence level.