Flavor-changing Majoron interactions with leptons

Yu Cheng,Xiao-Gang He,Cheng-Wei Chiang,Jin Sun

doi:10.1103/physrevd.104.013001

Abstract

When the Standard Model Higgs sector is extended with a complex singlet that breaks global lepton number symmetry spontaneously, a massless Goldstone boson called the Majoron J arises. In addition to increasing Higgs invisible decay through mixing, the Majoron can generally have flavor-changing interactions with fermions. We find that type-III seesaw model poses such interesting properties with both charged leptons and neutrinos. This opens up new channels to search for the Majoron. We use the experimental data such as muonium-anti-muonium oscillation and flavor-changing neutrino and charged lepton decays to put constraints on the couplings. As a novel way to reveal the chiral properties of these interactions, we propose an experimentally measurable polarization asymmetry of flavor-changing l to l' J decays.

Highlights

Since the discovery of the 125-GeV Higgs boson, it is an intriguing question whether there exists other elementary scalar bosons in nature
A class of models with an economical extension of the Higgs sector in the Standard Model (SM) involve the introduction of a SUð2ÞL × Uð1ÞY complex singlet S that induces the breakdown of global lepton number symmetry Uð1ÞL
Such models are of primary interest because they can generate neutrino mass [1] and house a Goldstone boson, generically called the Majoron J, from the spontaneous symmetry breaking triggered by the vacuum expectation value (VEV) of S

Summary

INTRODUCTION

Since the discovery of the 125-GeV Higgs boson, it is an intriguing question whether there exists other elementary scalar bosons in nature. We use Type-III seesaw model [6], with the VEV of a singlet to provide the heavy seesaw mass, as a simple explicit example to demonstrate the possibility of having flavorchanging interactions between the Majoron and the charged leptons. Such interactions alone will induce, for example, the μ → eJ decay, as considered a long time ago [7].

MAJORON IN TYPE-III SEESAW MODEL

V ν LR ν RR

CONSTRAINTS

POLARIZATION ASYMMETRY

Findings

CONCLUSION