CMS electromagnetic calorimeter calibration and alignment

Abstract

Precise calibration and alignment of the CMS electromagnetic calorimeter (ECAL) is crucial for achieving excellent ECAL performance required by many physics analyses employing electrons and photons. The methods used to inter-calibrate the ECAL energy response, using physics channels such as W/Z boson decays to electrons and π 0 ∕ η decays to photon pairs, and also exploiting the azimuthal symmetry of the minimum bias events are presented here. In addition, the details of the alignment procedure used to calibrate the position measurements in ECAL relative to the CMS Tracker is also described. Lastly, results of the calibration and alignment obtained with Run 2 data are presented. • Precise calibration and alignment of the CMS electromagnetic calorimeter (ECAL) is crucial for achieving the excellent ECAL performance required by many physics analyses employing electrons and photons. • This text describes the methods used to inter-calibrate the ECAL energy response, using physics channels such as W/Z boson decays to electrons and π 0 ∕ η decays to photon pairs, and also exploiting the azimuthal symmetry of the minimum bias events. • In addition, it details the alignment procedure used to calibrate the position measurements in ECAL relative to the CMS Tracker. • Results of the calibration and alignment obtained with Run 2 data are presented.