Abstract
The operation and performance of the Compact Muon Solenoid
(CMS) electromagnetic calorimeter (ECAL) are presented, based on
data 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 of
151 fb-1. The CMS ECAL is a scintillating lead-tungstate
crystal calorimeter, with a silicon strip preshower detector in the
forward region that provides precise measurements of the energy and
the time-of-arrival of electrons and photons. The successful
operation 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 new
phenomena. Precise calibration, alignment, and monitoring of the
ECAL response are important ingredients to achieve these goals. To
face the challenges posed by the higher luminosity, which
characterized the operation of the LHC in Run 2, the procedures
established during the 2011–2012 run of the LHC have been revisited
and new methods have been developed for the energy measurement and
for the ECAL calibration. The energy resolution of the calorimeter,
for electrons from Z boson decays reaching the
ECAL without significant loss of energy by bremsstrahlung, was
better 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 resulting
performance is similar to that achieved during Run 1 in 2011–2012,
in spite of the more severe running conditions.
