Comment on 'Induced Pseudoscalar Coupling Constant' by Il-Tong Cheon and Myung Ki Cheoun (nucl-th/9811009)

Abstract

In a recent preprint Cheon and Cheoun have derived from a chiral model an additional term, not usually appearing in the standard matrix element for radiative muon capture. Using that term they generate a large correction to the RMC spectrum which tends to resolve the problem caused by the too large value of $g_P$ found in the TRIUMF RMC experiment. In this comment we observe first that their extra term leads to an amplitude which is not gauge invariant and second that such a term should be present, in a gauge invariant way, in an earlier full chiral perturbation theory calculation, which however found negligible differences from the standard approach.