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

TL;DR

This study searches for a hypothetical light CP-odd Higgs boson in J/psi decays using a large dataset, setting new upper limits on its production and decay, thus constraining its possible properties.

Contribution

First search for a light CP-odd Higgs boson in J/psi radiative decays with improved upper limits, constraining its nature to be mostly singlet.

Findings

No evidence for the A^0 boson was found.

Set upper limits on the product branching fraction in the range of (2.8-495.3)×10^{-8}.

Limits are five times more stringent than previous results.

Abstract

We search for a light Higgs boson $A^0$ in the fully reconstructed decay chain of $J/\psi \rightarrow \gamma A^0$, $A^0 \rightarrow \mu^+\mu^-$ using $(225.0\pm2.8)\times10^6$ $J/\psi$ 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 $\mathcal{B}(J/\psi \rightarrow \gamma A^0) \times \mathcal{B}(A^0 \rightarrow \mu^+\mu^-)$ 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.