Seeking the CP-odd Higgs via $h\to {\eta }_{c,b}{\ell }^{+}{\ell }^{-}$

Abstract

We show that the decay rates of the Higgs boson to a pseudoscalar quarkonium and a pair of leptons, $h\to P{\ell }^{+}{\ell }^{-}$ ($P\in \{{\eta }_c,{\eta }_b\}$), can be substantially enhanced in a scenario with two Higgs doublets with a softly broken ${\mathbb{Z}}_2$ symmetry (2HDM) when the CP-odd Higgs A is light, i.e. $m_A\lesssim m_h$. Depending on the type of 2HDM the enhancement of $\mathcal{B}(h\to {\eta }_{c,b}{\tau }^{+}{\tau }^{-})$ with respect to its Standard Model value can be an order of magnitude larger, i.e. $\mathcal{O}(10^{-6}÷10^{-5})$. The decays $h\to P{\ell }^{+}{\ell }^{-}$ could therefore provide an efficient channel to investigate the presence of a light CP-odd Higgs $A$ and help to disentangle among various 2HDM scenarios.

Comments: 19 pages, 6 figures