Neutral Pion rejection for isolated and unconverted photon candidates using CMS ECAL and Preshower detector

Abstract

Applying a general Artificial Neural Network approach, the possibility to discriminate neutral pions (π0) from photons was studied using information from both ECAL and Preshower subdetectors. For unconverted particles the obtained neutral pion rejection could vary between 29% and 76% depending on the method used for selecting unconverted particles, the transverse energy and the pseudorapidity. The test of the algorithm on H → γγ and γ + Jet events showed that, in case of both photons are unconverted, the γ + Jet background could be reduced by 46% to 57% maintaining almost 85% to 88% of the Higgs events respectivly and this depends on the choise of the unconversion method used.