Performance and operation of the CMS electromagnetic calorimeter

The properties of a Higgs boson candidate are measured in the H→ZZ→4l decay channel, with l=e,μ, using data from pp collisions corresponding to an integrated luminosity of 5.1 inverse femtobarns at center-of-mass energy of s√=7 TeV and 19.7 inverse femtobarns at s√=8 TeV, recorded with the CMS detector at the LHC. The new boson is observed as a narrow resonance with a local significance of 6.8 standard deviations, a measured mass of 125.6±0.4 (stat.) ±0.2 (syst.) GeV, and a total width less than 3.4 GeV at a 95% confidence level. The production cross section of the new boson times the branching fraction to four leptons is measured to be 0.93+0.26−0.23(stat.)+0.13−0.09 (syst.) times that predicted by the standard model. Its spin-parity properties are found to be consistent with the expectations for the standard model Higgs boson. The hypotheses of a pseudoscalar and all tested spin-one boson hypotheses are excluded at a 99% confidence level or higher. All tested spin-two boson hypotheses are excluded at a 95% confidence level or higher

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“…The result is 0.83 +0.31 −0.25 in the 0/1-jet category and 1.45 +0. 89 −0.62 in the dijet category. The best-fit values are shown in Fig.…”

Section: Signal Strengthmentioning

confidence: 96%

Measurement of the properties of a Higgs boson in the four-lepton final state

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2014

Phys. Rev. D

403

427

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“…All channels in the EB supermodules were calibrated with cosmic-ray muons [21]. After installation at the LHC, the "beam splash" events were used to improve further the EB and EE calibrations [10]. The intercalibration constants from each method were cross-checked for consistency and combined to provide a weighted average for the channel.…”

Section: Single-channel Intercalibration C Imentioning

confidence: 99%

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

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2013

J. Inst.

171

155

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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 √ s = 7 TeV with integrated luminosities of about 5 fb −1 . Crucial aspects of detector operation, such as the environmental stability, alignment, and synchronization, 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 |η| < 0.8) and is 2-5% elsewhere. The derived energy resolution for photons from 125 GeV 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.

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“…An electromagnetic crystal calorimeter (ECAL) [17] and a brass/ scintillator hadron calorimeter (HCAL) [18] surround the tracking volume and cover jηj < 3.0. A forward quartz-fibre Cherenkov hadron calorimeter [19] extends the coverage to jηj ¼ 5.2.…”

Section: Detector Descriptionmentioning

confidence: 99%

Measurement of four-jet production in proton-proton collisions ats=7 TeV

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2014

Phys. Rev. D

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Measurements of the differential cross sections for the production of exactly four jets in proton-proton collisions are presented as a function of the transverse momentum p T and pseudorapidity η, together with the correlations in azimuthal angle and the p T balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of 36 pb −1 . The cross section for exactly four jets, with two hard jets of p T > 50 GeV each, together with two jets of p T > 20 GeV each, within jηj < 4.7 is measured to be σ ¼ 330 AE 5ðstat:Þ AE 45ðsyst:Þ nb. It is found that fixed-order matrix element calculations including parton showers describe the measured differential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data.

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Performance and operation of the CMS electromagnetic calorimeter

Cited by 67 publications

References 20 publications

Measurement of the properties of a Higgs boson in the four-lepton final state

Measurement of the properties of a Higgs boson in the four-lepton final state

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

Measurement of four-jet production in proton-proton collisions ats=7 TeV

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