Radiative Muon Capture and Induced Pseudoscalar Coupling Constant in Nuclear Matter

Abstract

The recent TRIUMF experiment for ${\mu }^{-}p\to n{\nu }_{\mu }\gamma$ gave a surprising result that the induced pseudoscalar coupling constant $g_P$ was larger than the value obtained from ${\mu }^{-}p\to n{\nu }_{\mu }$ experiment as much as 44 %. Reexamining contribution of the axial vector current in electromagnetic interaction, we found an additional term to the matrix element which was used to extract the $g_P$ value from the measured photon energy spectrum. This additional term, which plays a key role to restore the reliability of $g_P(-0.88m_{\mu }^2)=6.77g_A(0)$, is shown to affect the $g_P$ quenching problems in nucleus.

Comments: 11 pages, 3 figures