On radiative muon capture in hydrogen

Abstract

We analyze the radiative capture of the negative muon in hydrogen using amplitudes derived within the chiral Lagrangian approach. Besides the leading and next to leading order terms, given by the well-known Rood-Tolhoek Hamiltonian, we extract from these amplitudes the corrections of the next order in 1/M (M is the nucleon mass). In addition, we estimate within the same formalism also the ∆(1232) isobar excitation effects and processes described by an anomalous Lagrangian. Using of the parameters of the model obtained from the analysis of the pion photoproduction, which restricts the arbitrariness of the πN ∆ and γN ∆ vertices off-shell, allows us to explain two times more of the discrepancy between the value g P CAC P of the induced pseudoscalar form factor g P , predicted by partial conservation of the axial current, and of g P extracted from the recent TRIUMF experiment, than the standard approach. Varying these parameters independently, one can remove the discrepancy completely.