Relativistic Effects in Muon Capture by Complex Nuclei

Abstract
Relativistic contributions to muon capture by complex nuclei are considered. For the total rate calculated for a Fermi gas in the closure approximation these contributions increase the rate by about 15% for elements between Ca and Pb. The neutron asymmetry (with respect to the muon spin direction) near the top of the neutron spectrum is decreased in magnitude from a value of about -0.4 to about -0.1 by these contributions. A calculation using the Fermi-gas model for N=Z indicates that the neutron asymmetry has a magnitude less than 0.15 for all neutron energies, a result which is in disagreement with experiment.