Bounds on majoron emission from muon to electron conversion experiments

TL;DR

This paper investigates how muon-to-electron conversion experiments can set bounds on majoron emission, a process predicted by models with spontaneously broken lepton number symmetry, by analyzing the energy spectrum modifications in muonic atoms.

Contribution

It introduces a method to derive bounds on muon-electron-majoron coupling from mu-e conversion experiments considering atomic binding effects.

Findings

Future experiments could set bounds comparable to current direct searches.

Binding effects significantly influence the muon decay spectrum in muonic atoms.

Potential to improve constraints on majoron-related processes.

Abstract

In models where lepton number is considered to be a spontaneously-broken global symmetry a massless Goldstone boson, the majoron (J), appears. We describe a procedure to explore the muon-electron-majoron coupling using the results from mu-e conversion search experiments. To accomplish that, we determine how the energy spectrum of the muon decay into an electron and a majoron is modified by binding effects in a muonic atom. We find that the future mu-to-e conversion experiments may be able to produce bounds on the mu->eJ rate which are comparable with the present ones from direct searches.