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 (SCI-Expanded) 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 (SCI-EXPANDED), Scopus
  • Keywords: Gamma detectors (scintillators, CZT, HPG, HgI etc), Calorimeters, Large detector systems for particle and astroparticle physics, RECONSTRUCTION, PERFORMANCE, SYSTEM
  • Dokuz Eylül University Affiliated: Yes


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.