Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at √ s = 8 TeV

Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Filipovic, Nicolas and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Karancsi, János and Molnár, József and Pálinkás, József and Makovec, Alajos and Ujvári, Balázs and Veres, Gábor (2015) Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at √ s = 8 TeV. JOURNAL OF INSTRUMENTATION, 10. ISSN 1748-0221

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Abstract

A description is provided of the performance of the CMS detector for photon reconstruction and identification in proton-proton collisions at a centre-of-mass energy of 8 TeV at the CERN LHC. Details are given on the reconstruction of photons from energy deposits in the electromagnetic calorimeter (ECAL) and the extraction of photon energy estimates. The reconstruction of electron tracks from photons that convert to electrons in the CMS tracker is also described, as is the optimization of the photon energy reconstruction and its accurate modelling in simulation, in the analysis of the Higgs boson decay into two photons. In the barrel section of the ECAL, an energy resolution of about 1% is achieved for unconverted or late-converting photons from H to gamma gamma decays. Different photon identification methods are discussed and their corresponding selection efficiencies in data are compared with those found in simulated events. The measurement of the photon purity is described for one set of photon identification criteria.

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