Quenching of the Cabibbo angle and total muon capture rates

The results of the calculations of the total muon capture rates in heavy nuclei taking into account the hyperfine effects and nucleon-velocity terms in the muon capture Hamiltonian are presented along with the experimental data to test the Salam–Strathdee idea of vanishing of the Cabibbo angle at large electromagnetic fields. It is shown that for heavy nuclei, both the above corrections are negligible and hence the anomalous capture rates on 93Nb, 235U, and 239Pu could be largely due to the vanishing of the Cabibbo angle.