Martin White

This thesis divides naturally into three parts. The first deals with the use of gravitational lensing as a probe of cosmology: an analysis of the limits on the cosmological constant that can be inferred from lensing statistics, paying particular attention to lensing models and sources of uncertainty; and an investigation into the use of lens systems as probes of a changing gravitational constant.

The second part is a report on investigations of the solar neutrino problem. Using extensive numerical calculations of the propagation of neutrinos through the sun and the response of the Homestake and Kamiokande detectors, the Homestake and Kamiokande data sets are utilized to investigate which models may or may not fit the data. The dependence of conclusions on the treatment of the data sets is discussed. The viability of some solar-model-based solutions to the problem is also investigated.

Part three deals with the search for the Higgs boson at the two proposed supercolliders: LHC and SSC. Calculations of previously unconsidered backgrounds to Higgs production in association with top, anti-top pairs are presented. Based on this a brief analysis of electromagnetic calorimetry requirements for an observable signal is discussed.