Extending the Standard Model: an upper bound for a neutrino mass from the rare decay K+ -> Pi+ neutrino antineutrino

TL;DR

This paper extends the Standard Model to include Dirac neutrino masses and uses rare decay data to set an upper bound of 5.5 MeV on neutrino mass, tighter than current direct bounds.

Contribution

It introduces a model extension with Dirac neutrino masses affecting rare decay rates, providing a new upper bound on neutrino mass from experimental data.

Findings

Neutrino mass upper bound of 5.5 MeV derived from decay data

Extension of the Standard Model with flavor-changing neutral currents

Neutrino mass limit is three times lower than direct experimental bounds

Abstract

The standard model seeming at a loss to account for the present experimental average rate for the rare decay K+ -> Pi+ neutrino antineutrino, I tackle the question with the extension of the Glashow-Salam-Weinberg model to an SU(2)left x U(1) gauge theory of J=0 mesons proposed by the author in [Phys. Lett. B 385 (1996) 198], in which, in addition, the neutrinos are given Dirac masses from Yukawa couplings to the Higgs boson. The latter triggers a new contribution to this decay through flavor changing neutral currents that arise in the quartic term of the symmetry breaking potential; it becomes sizeable for a neutrino mass in the $MeV$ range; the experimental upper limit for the decay rate translates into an upper bound of 5.5 MeV for the mass of the neutrino, three times lower than present direct bounds.