Search for a light CP-odd Higgs boson in the radiative decays of J/psi

Abstract

We search for a light Higgs boson $A^0$ in the fully reconstructed decay chain of $J/\psi \to \gamma A^0$, $A^0\to {\mu }^{+}{\mu }^{-}$ using $(225.0\pm 2.8)\times 10^6$ $J/\psi$ events collected by the BESIII experiment. The $A^0$ is a hypothetical CP-odd light Higgs boson predicted by many extensions of the Standard Model including two spin-0 doublets plus an extra singlet. We find no evidence for $A^0$ production and set $90\%$ confidence-level upper limits on the product branching fraction $\mathcal{B}(J/\psi \to \gamma A^0)\times \mathcal{B}(A^0\to {\mu }^{+}{\mu }^{-})$ in the range of $(2.8-495.3)\times 10^{-8}$ for $0.212\le m_{A^0}\le 3.0$ GeV/c${}^2$. The new limits are $5$ times below our previous results, and the nature of the $A^0$ is constrained to be mostly singlet.

7 pages, 5 figures, submitted to the Physical Review D (rapid communications)