Muon capture beyond V — A currents

Abstract

We show the relevance of muon capture in analyzing the structure of weak charged currents. The study is made using rotational invariance and the reality condition imposed by time-reversal invariance, without a definite neutrino helicity, as the only inputs. The longitudinal and transverse polarizations of the outgoing neutrino are connected to measurable observables. All magnitudes are related to four independent observables, chosen as the capture rate Γ, the average polarization P N, the longitudinal polarization P L N and the asymmetry α in the angular distribution of recoils.