"Figure 8 (right)" of "Measurement of light-by-light scattering and the Breit-Wheeler process, and search for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV"

Observed and expected 95% CL limits on the production cross section $\sigma(\gamma\gamma \rightarrow a \rightarrow \gamma\gamma)$ as a function of the ALP mass $m_{a}$. The uncertainties indicate regions containing 68 and 95% of the distribution of limits expected under the background-only hypothesis. The additional datasets indicate the expected ALP cross sections as a function of $m_{a}$ for decreasing photon couplings ($g_{a\gamma} = 0.3, 0.1, 0.05 TeV^{-1}$).