Muon-Decay Parameters from COHERENT

TL;DR

This paper shows how measurements of CEvNS at spallation sources can provide new insights into muon decay parameters, offering the first direct constraints and discussing future sensitivities and implications for fundamental interactions.

Contribution

It introduces the first direct constraint on muon decay Michel parameters using CEvNS data from COHERENT and explores future experimental and theoretical implications.

Findings

First direct constraint on Michel parameters from CEvNS data

Discussion of future sensitivities and potential for probing Lorentz structure

Application to other neutrino production mechanisms like pion decay

Abstract

We demonstrate that measurements of Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) at spallation sources are valuable probes of muon-decay physics. Using COHERENT data we derive the first direct constraint on the Michel parameters governing the $\bar\nu_\mu$ energy distribution. We also discuss future sensitivities, the implications for the Lorentz structure of the interactions mediating muon decay and the application to other neutrino-production mechanisms like pion decay.