UC Santa Barbara

Natural supersymmetry is one well-motivated theory that could explain the apparent fine-tuning of the Higgs potential in the standard model. Natural supersymmetry predicts the existence of higgsinos, fermionic partners of Higgs bosons, with mass not far from the electroweak scale. Such higgsinos should be producible with the CERN LHC. This thesis presents a search for higgsinos with 137 fb−1 of proton-proton collision data collected by the CMS experiment in final states with two Higgs bosons, each decaying via the process H → bb, and large missing transverse momentum. This search is sensitive to the casethe higgsinos are considerably heavier than the lightest supersymmetric particle. The observed event yields are consistent with standard model predictions, and the results are interpreted in simplified models to exclude electroweak production of nearly degenerate higgsinos with mass between 175 and 1025 GeV and production of higgsino in gluino decays with gluino mass up to 2330 GeV at the 95% confidence level. The analysis is also combined with other searches for electroweak supersymmetric particles to produce limits on more general models with higgsinos.