"The 95% CL upper limit on the ALP cross section" of "Measurement of light-by-light scattering and search for axion-like particles with 2.2 nb$^{-1}$ of Pb+Pb data with the ATLAS detector"

The 95% CL upper limit on the ALP cross section $\sigma_{\gamma\gamma\rightarrow a \rightarrow\gamma\gamma}$ for the $\gamma\gamma\rightarrow a \rightarrow \gamma\gamma$ process as a function of ALP mass m$_{a}$. The observed upper limit is shown as a solid black line and the expected upper limit is shown by the dashed black line with its $\pm1$ and $\pm2$ standard deviation bands. The discontinuity at $m_{a}=70 GeV$ is caused by the increase of the mass-bin width which brings an increase in signal acceptance.