A New Higgs Boson with Electron-Muon Flavor-Violating Couplings

Abstract

Recently, the CMS Collaboration performed a search on a new resonance decaying to $e^\pm\mu^\mp$ in the mass range of 110 GeV to 160 GeV. The search also hints a possible excess at 146 GeV with a $3.8\sigma~(2.8\sigma)$ of local (global) significance. Motivated by that, we try to interpret the results in the context of the type-III two-Higgs-doublet-model. We find that the excess is only moderately constrained by low-energy lepton-flavor-violation processes, in particular the $\mu\to e \gamma$ decay. We also compare the CMS bounds across the entire search region against constraints of $\mu\to e\gamma$ and $\mu\to e$ conversion in nuclei. Our finding indicates that the collider bounds can be superior to those of low-energy processes for the scalar mass between $110 \text{ GeV}$ and $150 \text{ GeV}$, suggesting the importance of this mass range for future searches.