Polarized Muon Decay at Rest with V+A Interaction

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.

CP Violation in Antineutrino-Electron Elastic Scattering

Elastic scattering of transversely polarized electron antineutrino beam off unpolarized electrons can be used to detect the CP-violating effects by measuring the azimuthal asymmetry of recoil electrons caused by the interference terms between the standard vector $c_{V}^{L}$, axial $c_{A}^{L}$ couplings of left-chirality antineutrinos and exotic scalar $c_{S}^{R}$ coupling of right-chirality ones in the differential cross section. It would be a positive evidence for the existence of the exotic antineutrino states. Moreover, we also show that the differential cross section for the $overline{ u} e^- $ scattering can be obtained from the one for the $ u e$ scattering, if one makes the substitution $c_{T}^{R} to -c_{T}^{R}$, $c_{A}^{L} to -c_{A}^{L}$, ${bf q}to -{bf q}$, ${boldmath $hat{eta}_{ u}$}to -{boldmath $hat{eta}_{ u}$}$.