Comparison of theNm16(0−)β-Decay Rate with the Inverse Muon-Capture Rate: The Induced Pseudoscalar Form Factor in Nuclei

Abstract

We report on the observation of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}_{}^m{}_{}{}^{}\left(0^{-}\right)\to {}_{}{}^{16}{}_{}{}^{}\mathrm{O}(\mathrm{g}.\mathrm{s}.\mathrm{})$ $\beta$ decay. The comparison of the measured decay rate, 0.43±0.10 ${\sec }^{-1\mathrm{}}$, with the rate of the inverse muon-capture reaction in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ yields for the induced-pseudoscalar form factor: $13<~g_P\left(q^2\simeq {m_{\mu }}^2\right)<~20$. Subject to the approximations of the analysis and neglecting possible second-class currents, this result indicates an upward renormalization of this form factor in nuclei.