Probing the doubly-charged Higgs with Muonium to Antimuonium Conversion Experiment

TL;DR

This paper explores how the upcoming MACE experiment can detect muonium to antimuonium conversion, providing a new way to probe models with doubly-charged Higgs particles that are difficult to observe with current collider and flavor experiments.

Contribution

It assesses MACE's potential to detect doubly-charged Higgs effects in neutrino mass models, surpassing current experimental limits.

Findings

MACE can probe parameter space beyond LHC reach.

Muonium-antimuonium conversion is sensitive to doubly-charged Higgs effects.

The study sets prospects for future experimental searches.

Abstract

The spontaneous muonium-to-antimuonium conversion is one of the interesting charged lepton flavor violation processes. MACE is the next generation experiment to probe such a phenomenon. In models with a triplet Higgs to generate neutrino masses, such as Type-II seesaw and its variant, this process can be induced by the doubly-charged Higgs contained in it. In this article, we study the prospect of MACE to probe these models via the muonium-to-antimuonium transitions. After considering the limits from $\mu^+ \rightarrow e^+ \gamma $ and $\mu^+ \rightarrow e^+ e^- e^+$, we find that MACE could probe a parameter space for the doubly-charged Higgs which is beyond the reach of LHC and other flavor experiments.