Explaining the CMS Higgs flavor violating decay excess

TL;DR

This paper explores whether the Type-III 2HDM can explain a 2.5σ excess in CMS's lepton flavor violating Higgs decay to tau and muon, consistent with other experimental constraints.

Contribution

It demonstrates that the Type-III 2HDM can account for the observed excess while satisfying various theoretical and experimental constraints.

Findings

Type-III 2HDM can reproduce the CMS excess.

Allowed signal strength for standard channels decreases with BR(h→τμ)~1%.

Future measurements can test this model if the excess persists.

Abstract

Direct searches for lepton flavor violating Higgs boson decays in the $\tau \mu$ channel have been recently reported by the CMS collaboration. The results display a slight excess of signal events with a significance of 2.5$\sigma$, which translates into a branching ratio of about $1$%. By interpreting these findings as a hint for beyond the standard model physics, we show that the Type-III 2HDM is capable of reproducing such signal while at the same time satisfying vacuum stability, perturbativity, electroweak precision data, measured Higgs standard decay modes and low-energy lepton flavor violating constraints. We have found that the allowed signal strength ranges for the $b\bar b$, $WW^*$ and $ZZ^*$ standard channels shrink as soon as BR$(h\to\tau\mu)\sim 1$% is enforced. Thus, we point out that if the excess persists, improved measurements of these channels may be used to test our Type-III 2HDM scenario.