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.

Los Angeles County is home to the country’s largest child welfare system and the state of California’s largest undocumented population. While a considerable amount of research exists for each population, very little is known about how these two populations intersect. This study seeks to explore the qualitative experiences of undocumented foster youth, with the aim of understanding what types of institutional barriers exist and how they affect academic, physical and mental health, and placement outcomes for these youth. Using Critical Race Theory and Legal Violence frameworks, the study utilizes two methods of inquiry: semi-structured interviews with various key stakeholders representing the fields of social welfare, law, and community advocacy; and a testimonio with a former foster youth who was undocumented during her time in care. After a collaborative analysis with the former foster youth, results indicate that there are numerous structural barriers for undocumented foster youth, including issues with policy, mental health and medication, lack of support, racism and prejudice, barriers to reunification, and alienation and exclusion due to having undocumented status. Implications for policy and practice are discussed.