Right-handed chirality of muon neutrinos in polarized muon decay at rest

Abstract

In this paper, we analyze the polarized muon decay at rest admitting the non-standard V + A interaction in addition to the standard V − A interaction. We show that the angle-energy distribution of Dirac muon neutrinos (ν μ ') is sensitive to the interference terms between the standard V − A coupling of left-chirality ν μ and exotic V + A coupling of right-chirality one, which are proportional to the transverse components of ν μ spin polarization. The interferences do not vanish in the limit of massless ν μ and include the relative phases to test the CP violation. It allows one to calculate a neutrino flux for an assumed configuration of detector in the case of standard model prediction, and the upper limits on the neutrino flux for the left-right ν μ mixture. It is also demonstrated that the effects of neutrino mass and mixing are tiny corrections and can be omitted. The most important conclusion is that even in the massless ν μ limit, there are physical effects connected with the mixture of left-and righthanded helicity components in a spin 1/2 quantum state, when the exotic interaction V + A is admitted, contrary to the electron observables, where all the possible interferences vanish.