Decay of the vortex muon

TL;DR

This paper explores how muons in vortex states with orbital angular momentum decay differently, revealing new polarization features through electron spectra, which can be used to distinguish vortex muons from plane wave muons.

Contribution

It introduces the analysis of muon decay in vortex states, showing how electron spectra can reveal polarization and orbital angular momentum effects.

Findings

Electron spectra are significantly modified in vortex muon decays.

Vortex muons can be distinguished from plane wave muons via fixed-angle electron spectra.

These features enable tracking vortex muons in magnetic fields.

Abstract

Muon decay is self-analyzing: the spectral-angular distribution of the emitted electron reveals the spin orientation of the polarized muon. Here, we show that the same feature applies to muons in non-plane-wave states and helps reveal the rich polarization opportunities available. We focus on the so-called vortex states, in which the muon carries a non-zero orbital angular momentum with respect to the average propagation direction and exhibits a cone structure in the momentum distribution. We compute the spectrum and the angular distribution of the electrons emitted in decays of vortex muons and show that the most revealing observable is not the angular distribution but the fixed-angle electron spectra. Even for very small cone opening angles of the vortex muons, it will be easy to observe significant modifications of the electron spectra which would allow one to distinguish vortex muons from approximately plane wave muons, as well as to differentiate among various polarization states. These features will be the key to tracking the evolution of vortex muons in external magnetic fields.