Nuclear Muon Capture in Extreme Kinematics

The results of two experiments, which measured the rates and energy spectra of charged particles emitted following negative muon capture by nuclei are presented in this thesis. In these experiments, we attempted to detect the highest energy charged particles allowed by the kinematics of the muon capture reaction. The measurement of these high energy charged particles probes the extreme kinematic region of muon capture where the neutrino energy is small. In this region, muon capture is particularly sensitive to nucleon-nucleon correlations, meson exchange currents, and high momentum components in the nuclear wave function. In the first experiment described in this thesis, we measured the energy spectra of high energy protons emitted following muon capture by carbon, calcium and yttrium. Because protons cannot be produced in the primary muon capture reaction, they are much more sensitive to muon capture by correlated pairs of nucleons. Our analyses of these spectra show that a few hundredths of a percent of the muon captures feature a proton emitted with an energy above 40 MeV. A detailed analysis of muon capture by calcium shows that our proton spectrum and the previously measured high energy neutron spectrum are consistent only after assuming a capture mechanism that includes two (or more) bodies. In the second experiment, we measured the rate and energy spectra of the swift protons and deuterons emitted following muon capture by ^3He. Because of the availability of good three body wave functions for ^3He, our measurements should illuminate the importance of proper inclusion of meson exchange currents in an exact microscopic calculation of the capture reaction. We compare our results to a plane wave impulse approximation (PWIA) model calculation, which we performed. We find that the proton spectrum is in fair agreement with the PWIA model. However, the same model underpredicts the deuteron spectrum by a large factor.