Polarized Muon Decay at Rest with V+A Interaction

TL;DR

This paper investigates how non-standard V+A interactions affect polarized muon decay at rest and neutrino-electron scattering, revealing interference effects that could help detect CP violation and new physics beyond the standard model.

Contribution

It introduces a detailed analysis of V+A interactions in polarized muon decay and neutrino scattering, highlighting interference effects and CP violation tests.

Findings

Interference terms depend on transverse neutrino polarization.

CP violation phases influence neutrino flux and event rates.

V+A interactions modify standard model predictions in neutrino processes.

Abstract

In this paper, we analyze the polarized muon decay at rest (PMDaR) and elastic neutrino-electron scattering (ENES) admitting the non-standard V+A interaction in addition to standard V-A interaction. Considerations are made for Dirac massive muon neutrino and electron antineutrino. Moreover, muon neutrinos are transversely polarized. It means that the outgoing muon-neutrino beam is a mixture of the left- and right-chirality muon neutrinos and has a fixed direction of transverse spin polarization with respect to production plane. We show that the angle-energy distribution of muon neutrinos contains the interference terms between the standard V-A and exotic V+A couplings, which are proportional to the transverse components of muon neutrino spin polarization. They do not vanish in a limit of massless neutrino and include the relative phases to test the CP violation. In consequence, it allows to calculate a neutrino flux and an expected event number in the ENES (detection process) both for the standard model prediction and the case of neutrino left-right mixture.