$H\to \ell\ell'$ in the Simplest Little Higgs Model

Abstract

Little Higgs Models are promising constructs to solve the hierarchy problem affecting the Higgs boson mass for generic new physics. However, their preservation of lepton universality forbids them to account for the $H\to\tau\mu$ CMS hint and at the same time respect (as they do) the severe limits on $H\to\mu e$ inherited from the non-observation of $\mu\to e\gamma$. We compute the predictions of the Simplest Little Higgs Model for the $H\to \ell\ell'$ decays and conclude that the measurement of any of these decays at LHC (even with a much smaller rate than currently hinted) would, under reasonable assumptions, disfavor this model. This result is consistent with our earlier observation of very suppressed lepton flavor violating semileptonic tau decays within this model.