Search for di-photon decays of an axion-like particle in radiative $J\mathrm{/}\psi$ decays

We search for the di-photon decay of a light pseudoscalar axion-like particle, $a$, in radiative $J\mathrm{/}\psi$ decays, using 10 billion $J\mathrm{/}\psi$ events collected with the BESIII detector. We find no evidence of a signal and set upper limits at the $95\mathrm{\%}$ confidence level on the product branching fraction $\mathcal{B}(J\mathrm{/}\psi \to \gamma a)\times \mathcal{B}(a\to \gamma \gamma )$ and the axion-like particle photon coupling constant $g_{a\gamma \gamma }$ in the ranges of $(3.7-48.5)\times {10}^{-8}$ and $(2.2-101.8)\times {10}^{-4}$ GeV${}^{-1}$, respectively, for $0.18\le m_a\le 2.85$ GeV/$c^2$. These are the most stringent limits to date in this mass region.