Updated constraints from radiative $\Upsilon$ decays on a light CP-odd Higgs

Abstract

The possible existence of a light CP-odd Higgs state in many new-physics models could lead to observable effects in the bottomonium sector. Experimental bounds on radiative $\Upsilon$ decays through such a pseudoscalar state and possible mixings with the $\eta_b^0$ states are reviewed. Combining these two effects, we set constraints on the properties of the CP-odd Higgs in the limit of small photon energy of $BR(\Upsilon\to\gamma\,\tau^+\tau^-)$, that is on the pseudoscalar mass-range $\sim8-10$GeV.