Abstract
The performance is presented of the reconstruction and identification algorithms for electrons and photons with the CMS experiment at the LHC.The reported results are based on proton-proton collision data collected at a center-of-mass energy of 13 TeV and recorded in 2016–2018, corresponding to an integrated luminosity of 136 fb^-1. Results obtained from lead-lead collision data collected at √(sNN)=5.02 TeV are also presented. Innovative techniques are used to reconstruct the electron and photon signals in the detector and to optimize the energy resolution. Events with electrons and photons in the final state are used to measure the energy resolution and energy scale uncertainty in the recorded events.The measured energy resolution for electrons produced in Z boson decays in proton-proton collision data ranges from 2 to 5%, depending on electron pseudorapidity and energy loss through bremsstrahlung in the detector material.The energy scale in the same range of energies is measured with an uncertainty smaller than 0.1 (0.3)% in the barrel (endcap) region in proton-proton collisions and better than 1 (3)% in the barrel (endcap) region in heavy ion collisions.The timing resolution for electrons from Z boson decays with the full 2016–2018 proton-proton collision data set is measured to be 200 ps.
Highlights
Electrons and photons are reconstructed with high purity and efficiency in the CMS experiment, one of the two general-purpose detectors operating at the CERN LHC [1]
Once the track candidates are reconstructed by the Kalman filter (KF) algorithm, their parameters are estimated at each layer with a Gaussian sum filter (GSF) fit in which the energy loss is approximated by an admixture of Gaussian distributions [4]
The performance of electron and photon reconstruction and identifica√tion in CMS during LHC Run 2 was measured using data collected in proton-proton collisions at s = 13 TeV in 2016–2018 corresponding to a total integrated luminosity of 136 fb−1
Summary
Electrons and photons are reconstructed with high purity and efficiency in the CMS experiment, one of the two general-purpose detectors operating at the CERN LHC [1]. These electromagnetically interacting particles leave a distinctive signal in the electromagnetic calorimeter (ECAL) as an isolated energy deposit that is associated with a trace in the silicon tracker in the case of electrons. These properties, together with the excellent energy resolution of the ECAL, make electrons and photons ideal to use both in precision measurements and in searches for physics beyond the standard model with the CMS detector.
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