An improved upper limit for the (muon based) neutrino mass

TL;DR

This paper refines the upper limit on the muon-based neutrino mass to 0.021 MeV by analyzing muon decay width within the V-A theory, assuming low electron neutrino mass, and discusses limitations for tau neutrino mass constraints.

Contribution

It provides an improved upper limit on the muon neutrino mass using decay width analysis, considering recent experimental data and theoretical assumptions.

Findings

Muon decay width constrains muon neutrino mass to 0.021 MeV.

Agreement with experimental data is maintained with the new constraint.

Constraints for tau neutrino mass are not feasible due to larger experimental errors.

Abstract

The width for the mu decay is calculated in the V-A theory leaving open the possibility of non zero neutrino masses. It is shown that not only the agreement with the experimental data is kept, but the smallness of the experimental error allows to improve the constraint of nu mass (muon based) down to 0.021 MeV, provided that nu mass (electron based) is as low as indicated by the 3H beta decay. An analogous constraint for the nu mass (tau based) is not possible since in this case the decay width has a larger experimental error.