Massive Neutrino Decays

TL;DR

This paper introduces the Feynman loop-diagram method using neutrino decay as an example, highlighting potential decay modes of massive neutrinos and their quantum loop effects.

Contribution

It provides an elementary introduction to Feynman loop-diagrams and decay rate calculations through the specific case of neutrino decays.

Findings

Massive neutrinos could decay into lighter neutrinos and photons.

Decay modes include radiative and tree-level processes.

Quantum loop effects can significantly enhance certain decay channels.

Abstract

Neutrino physics is used as an illustrative example for an elementary introduction to the computational method of Feynman loop-diagrams and decay rates. If the neutrinos are as massive as recently reported by the Super-Kamiokande results, the heaviest neutrino $\nu_H$ would not be stable. Although chargeless, it could decay -- by quantum loop effect -- into a lighter neutrino $ \nu_L$ by emitting a photon: $\nu_H \to \nu_L + \gamma $. If kinematically possible, the $\nu_H \to \nu_L$ + e$^+$ + e$^-$ mode could occur at the tree diagram level and furthermore get enhanced, at one-loop radiative corrections, by a large logarithm of the electron mass acting as an infrared cutoff.