Reconstruction of neutral pions from photon conversions

In this study, the low energetic photon conversion process in the ATLAS detector has been discussed. The conversion candidates selected from minimum bias events at √s=8 TeV are used to reconstruct π^0 particles built from two-photon invariant mass distribution. A clear π^0 peak is obtained and fitted to Gaussian function. The results reveal that purity of the π^0 signal depends strongly on the χ^2 value of the e^+ e^- pairs. It is also found that the optimal mass window cut for selecting π^0 candidates is around ±2σ around the π^0 peak.