Performance of the CMS electromagnetic calorimeter in pp collisions at √$_{s}$ = 13 TeV
The operation and performance of the Compact Muon Solenoid(CMS) electromagnetic calorimeter (ECAL) are presented, based ondata collected in pp collisions at√$_{s}$ =13 TeV at the CERN LHC, in the years from 2015 to 2018(LHC Run 2), corresponding to an integrated luminosity of151 fb$^{-1}$. The CMS ECAL is a scintillating lead-tungstatecrystal calorimeter, with a silicon strip preshower detector in theforward region that provides precise measurements of the energy andthe time-of-arrival of electrons and photons. The successfuloperation of the ECAL is crucial for a broad range of physics goals,ranging from observing the Higgs boson and measuring its properties,to other standard model measurements and searches for newphenomena. Precise calibration, alignment, and monitoring of theECAL response are important ingredients to achieve these goals. Toface the challenges posed by the higher luminosity, whichcharacterized the operation of the LHC in Run 2, the proceduresestablished during the 2011–2012 run of the LHC have been revisitedand new methods have been developed for the energy measurement andfor the ECAL calibration. The energy resolution of the calorimeter,for electrons from Z boson decays reaching theECAL without significant loss of energy by bremsstrahlung, wasbetter than 1.8%, 3.0%, and 4.5% in the |η| intervals[0.0,0.8], [0.8,1.5], [1.5, 2.5], respectively. This resultingperformance is similar to that achieved during Run 1 in 2011–2012,in spite of the more severe running conditions.