Radiative Muon Capture in Calcium

The branching ratio relative to ordinary muon capture and the photon asymmetry relative to the muon-spin direction were measured for radiative muon capture in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. For ~ 1200 photon events, the partial branching ratio is $R_{k>\mathrm{}57\mathrm{} \mathrm{MeV}}=(21.1\mathrm{}\pm 1.4)\times {10}^{-6\mathrm{}}$, and the asymmetry for $k>\mathrm{}63.5\mathrm{}$ MeV is +0.90±0.50. A fit of the photon spectrum to the theory of Rood, Yano, and Yano gives the value ${g_P}^{\mu }=(6.5\mathrm{}\pm 1.6)g_A$ for the pseudoscalar-coupling constant. These results are in disagreement with earlier experiments.