Energy calibration and resolution of the CMS electromagnetic calorimeter in pp collisions at sqrt(s) = 7 TeV
S. Chatrchyan
,
M. Besançon
(1)
,
S. Choudhury
(1)
,
F. Couderc
(1)
,
M. Dejardin
(1)
,
D. Denegri
(1)
,
B. Fabbro
(1)
,
J.L. Faure
(1)
,
F. Ferri
(1)
,
S. Ganjour
(1)
,
A. Givernaud
(1)
,
P. Gras
(1)
,
G. Hamel de Monchenault
(1)
,
P. Jarry
(1)
,
E. Locci
(1)
,
J. Malcles
(1)
,
L. Millischer
(1)
,
A. Nayak
(1)
,
J. Rander
(1)
,
A. Rosowsky
(1)
,
M. Titov
(1)
,
S. Baffioni
(2)
,
F. Beaudette
(2)
,
L. Benhabib
(2)
,
L. Bianchini
(2)
,
M. Bluj
(2)
,
Pierre Busson
(2)
,
C. Charlot
(2)
,
N. Daci
(2)
,
T. Dahms
(2)
,
M. Dalchenko
(2)
,
L. Dobrzynski
(2)
,
A. Florent
(2)
,
R. Granier de Cassagnac
(2)
,
M. Haguenauer
(2)
,
P. Mine
(2)
,
C. Mironov
(2)
,
I.N. Naranjo
(2)
,
M. Nguyen
(2)
,
C. Ochando
(2)
,
P. Paganini
(2)
,
D. Sabes
(2)
,
R. Salerno
(2)
,
Y. Sirois
(2)
,
C. Veelken
(2)
,
A. Zabi
(2)
,
J.-L. Agram
(3)
,
J. Andrea
(3)
,
D. Bloch
(3)
,
D. Bodin
(3)
,
J.-M. Brom
(3)
,
E.C. Chabert
(3)
,
C. Collard
(3)
,
E. Conte
(3)
,
F. Drouhin
(3)
,
J.-C. Fontaine
(3)
,
D. Gele
(3)
,
U. Goerlach
(3)
,
C. Goetzmann
(3)
,
P. Juillot
(3)
,
A.-C. Le Bihan
(3)
,
P. van Hove
(3)
,
S. Gadrat
(4)
,
S. Beauceron
(5)
,
N. Beaupere
(5)
,
G. Boudoul
(5)
,
S. Brochet
(5)
,
J. Chasserat
(5)
,
R. Chierici
(5)
,
D. Contardo
(5)
,
P. Depasse
(5)
,
H. El Mamouni
(5)
,
J. Fay
(5)
,
S. Gascon
(5)
,
M. Gouzevitch
(5)
,
B. Ille
(5)
,
T. Kurca
(5)
,
M. Lethuillier
(5)
,
L. Mirabito
(5)
,
S. Perries
(5)
,
L. Sgandurra
(5)
,
V. Sordini
(5)
,
Y. Tschudi
(5)
,
M. Vander Donckt
(5)
,
P. Verdier
(5)
,
S. Viret
(5)
S. Chatrchyan
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Pierre Busson
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R. Granier de Cassagnac
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C. Mironov
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P. Paganini
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J.-L. Agram
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C. Collard
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E. Conte
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P. van Hove
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M. Gouzevitch
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M. Lethuillier
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V. Sordini
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P. Verdier
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Abstract
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 sqrt(s)=7 TeV with integrated luminosities of about 5 inverse femtobarns. 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 abs(eta)<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 entraps. The calibration of the absolute energy is determined from Z to e+e- decays to a precision of 0.4% in the barrel and 0.8% in the endcaps.