Energy calibration and resolution of the CMS electromagnetic calorimeter in pp collisions at root s=7 TeV

Chatrchyan S., Khachatryan V., Sirunyan A. M. , Tumasyan A., Adam W., Bergauer T., ...More

JOURNAL OF INSTRUMENTATION, vol.8, 2013 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 8
  • Publication Date: 2013
  • Doi Number: 10.1088/1748-0221/8/09/p09009
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Keywords: Gamma detectors (scintillators, CZT, HPG, HgI etc), Calorimeters, Large detector systems for particle and astroparticle physics, RECONSTRUCTION, PERFORMANCE, SYSTEM


The energy calibration and resolution of the electromagnetic calorimeter (ECAL) of the CMS detector have been determined using proton-proton collision data from LHC operation in 2010 and 2011 at a centre-of-mass energy of root s = 7 TeV with integrated luminosities of about 5 fb(-1). Crucial aspects of detector operation, such as the environmental stability, alignment, and synchronozation, are presented. The in-situ calibration procedures are discussed in detail and include the maintenance of the calibration in the challenging radiation environment inside the CMS detector. The energy resolution for electrons from Z-boson decays is better than 2% in the central region of the ECAL barrel (for pseudorapidity vertical bar eta vertical bar < 0.8) and is 2-5% elsewhere. The derived energy resolution for photons from 125GeV Higgs boson decays varies across the barrel from 1.1% to 2.6% and from 2.2% to 5% in the endcaps. The calibration of the absolute energy is determined from Z -> e(+)e(-) decays to a precision of 0.4% in the barrel and 0.8% in the endcaps.