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

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 $\hat{I}{¼}^{+}\to e^{+}{\hat{I}}^3$ and $\hat{I}{¼}^{+}\to e^{+}{e}^{-}{e}^{+}$, 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.

12 pages, 2 figures