Weak decay of magnetized pions

TL;DR

This paper investigates how strong magnetic fields affect the decay of charged pions, revealing significant enhancements in muonic decay rates and introducing new decay constants through non-perturbative lattice calculations.

Contribution

It provides the first non-perturbative lattice calculation of magnetic field-dependent decay constants for charged pions, including the effects of Lorentz symmetry breaking.

Findings

Muon decay rate is drastically enhanced in strong magnetic fields.

New decay constants associated with vector current are introduced and calculated.

Results have potential implications for astrophysical phenomena.

Abstract

The leptonic decay of charged pions is investigated in the presence of background magnetic fields. In this situation Lorentz symmetry is broken and new fundamental decay constants need to be introduced, associated with the decay via the vector part of the electroweak current. We calculate the magnetic field-dependence of both the usual and a new decay constant non-perturbatively on the lattice. We employ both Wilson and staggered quarks and extrapolate the results to the continuum limit. With this non-perturbative input we calculate the tree-level electroweak amplitude for the full decay rate in strong magnetic fields. We find that the muonic decay of the charged pion is enhanced drastically by the magnetic field. We comment on possible astrophysical implications.