A study of neutral particle decay in magnetic field with the "Worldline Instanton" approach

TL;DR

This paper applies the worldline instanton semiclassical approach to analyze neutrino decay into electrons and W-bosons in magnetic fields, deriving the effective threshold energy and discussing astrophysical implications.

Contribution

It introduces a novel application of the worldline instanton method to neutral particle decay in magnetic fields, using a scalar toy model for leading exponential calculations.

Findings

Determines the effective threshold energy as a function of magnetic field.

Shows the method's general applicability to neutral particle decay in electromagnetic fields.

Provides insights relevant to astrophysical phenomena involving magnetic fields.

Abstract

We study the process of neutrino decay to electron and $W$-boson in the external magnetic field using the semiclassical "worldline instanton" approach. Being interested only in the leading exponential factor, we make calculations in a toy model, treating all particles as scalars. This calculation determines the effective threshold energy of the reaction as a function of the magnetic field. Possible astrophysical applications are discussed. It is emphasized that the method is general and is applicable to a decay of an arbitrary neutral particle into charged ones in the external electromagnetic field.