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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 ( $$\nu _{\mu }$$ ') is sensitive to the interference terms between the standard $$V-A$$ coupling of left-chirality $$\nu _{\mu }$$ and exotic $$V+A$$ coupling of right-chirality one, which are proportional to the transverse components of $$\nu _{\mu }$$ spin polarization. The interferences do not vanish in the limit of massless $$\nu _{\mu }$$ 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 $$\nu _{\mu }$$ 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 $$\nu _{\mu }$$ limit, there are physical effects connected with the mixture of left- and right-handed 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. [ABSTRACT FROM AUTHOR]

We propose a new method, using the Andreev reflection at superconductors, to measure parity violation induced by the standard electroweak theory, which in turn constrains the possible parity-violating effects of new physics. The weak neutral currents induce parity-violating, marginal effective operators, though quite tiny, in superconductors. We estimate their effects on superconducting gaps and propose a method to measure the parity-violation from the spin polarization effect, when electrons or holes get Andreev-reflected at the interface between normal metal and a superconductor. Such polarization effects might be comparable to the atomic parity violation and thus naturally give an interesting bound on certain models of new physics, that couples to electrons, such as Majorana mass of active neutrinos or doubly charged Higgs. [ABSTRACT FROM AUTHOR]