$\pi^0$ rejection in the FCC electromagnetic calorimeter

The separation of photons and $\pi^0$ mesons in the electromagnetic calorimeter of the Future Circular Collider was investigated using various geometries for particle energies in the range of 10 GeV to 80 GeV. This study is based on simulated events of single particles without electronic noise or pileup and analyzed using the boosted decision tree algorithm. For the baseline geometry, a $\pi^0$ rejection factor of $R_{\pi} = 3.22 \pm 0.14$ at $p_{T} = 50$ GeV with $\gamma$ signal efficiency of $90 \pm$ 1 $\%$ was obtained considering 20 cm depth and 3 layers of the EM calorimeter barrel. In analyzing other geometries, the layer thicknesses were altered but total depth was kept constant and the rejection factor was increased to $R_{\pi} = 4.18 \pm 0.20$ when considering 5 layers with segmentation of $0.0025 \times 0.0045$ $(\Delta\eta \times \Delta\phi)$ in the $2^{nd}$ layer and $0.01 \times 0.0045$ in the others. Overall $\pi^0$ rejection factor of $R_{\pi} = 3.58 \pm 0.16$ was calculated for $p_T \in [10 - 80]$ GeV and $|\eta| = 0$. The discriminating variables for this analysis were inspired by previous investigation on $\gamma$/$\pi^0$ separation in the ATLAS electromagnetic calorimeter and the obtained results are compared with this study.