Equation of spin motion for a particle with electric and magnetic charges and dipole moments

TL;DR

This paper derives a comprehensive classical equation for the spin motion of particles with electric and magnetic charges and dipole moments, relevant for understanding potential dark matter interactions.

Contribution

It provides the first rigorous derivation of the spin motion equation for particles with both electric and magnetic charges and dipole moments in electromagnetic fields.

Findings

Derived the general classical spin motion equation.

Obtained the spin motion equation relative to momentum in storage rings.

Highlighted relevance to dark matter axion-induced CP violation.

Abstract

The general classical equation of spin motion is rigorously derived for a particle with electric and magnetic charges and dipole moments in electromagnetic fields. The equation describing the spin motion relative to the momentum direction in storage rings is also obtained. The importance of the derivation follows from a possible appearance of magnetic charges and EDMs due to the pseudoscalar \emph{CP}-violating electromagnetic interaction caused by dark matter axions.