Majoron emission in muon and tau decays revisited

TL;DR

This paper investigates the theoretical predictions and experimental prospects for detecting Majoron emission in muon and tau decays within supersymmetric models with spontaneous R-parity breaking, highlighting its potential to reveal lepton number violation.

Contribution

It provides the first detailed calculation of Majoron-emitting decay branching ratios in supersymmetric models with spontaneous R-parity breaking, linking them to neutralino decay modes and experimental observables.

Findings

Br($ o e J$) can be maximized in specific parameter regions.

Measurement of Br($ o e J$) can provide insights into R-parity violation.

Current bounds and future sensitivities for Majoron couplings are discussed.

Abstract

In models where the breaking of lepton number is spontaneous a massless Goldstone boson, the Majoron ($J$), appears. We calculate the theoretically allowed range for the branching ratios of Majoron emitting charged lepton decays, such as Br($\mu \to e J$) and Br($\mu \to e J \gamma$), in a supersymmetric model with spontaneous breaking of R-parity. Br($\mu\to eJ$) is maximal in the same region of parameter space for which the lightest neutralino decays mainly invisibly. A measurement of Br($\mu\to eJ$) thus potentially provides information on R-parity violation complementary to accelerator searches. We also briefly discuss existing bounds and prospects for future improvements on the Majoron coupling to charged leptons.