CERN-THESIS-2012-153 26/07/2012 - CERN Document Server

Identification efficiency
eff id
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­2.5 ­2 ­1.5 ­1 ­0.5 0 0.5 1 1.5 2 2.5
(a)
Identification efficiency
eff id
1
0.8
0.6
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0
× 10
20 40 60 80 100 120 140 160 180 200
Figure 5.3: Muon identification efficiency for data (black dots) and MC (yellow rectangles), as a function
of (a) η(µ) and (b) pT(µ). The data uses 0.7 fb −1 of 2011 collision data. The MC includes all background
contributions.
Momentum Scale and Resolution
At the same time, the scale and resolution of the muon momentum distributions are corrected on MC, to
match those observed in data. This is done for the inner detector and the muon spectrometer tracks used
in the muon combined track separately. This correction is done before the selection of muons.
5.3.2 Electrons
Electron candidates are found as clusters in the EM calorimeter, with a matching track in the inner detector.
Additional cuts on shower shapes (lateral and longitudinal shower profiles) and on information from the re-
constructed track are applied to further reject fake electrons (e.g. photons). Stringent quality requirements
on conditions of the EM calorimeter at the time of the data taking are applied to ensure a well measured
energy. A tight selection using calorimeter, tracking and combined variables is used to provide good separa-
tion between signal electrons and background. As for muons, electrons are required to have high transverse
momentum and be isolated in order to suppress backgrounds from misidentified jets. Electron candidates
are required to have ET > 20 GeV where ET is constructed as ET = Ecluster/cosh(ηtrack), meaning from the
calorimeter cluster energy Ecluster and the direction of the electron track, ηtrack. The isolation requirement
is calorimeter-based only: the transverse energy deposited in the calorimeter not associated to the electron
is summed in a cone of radius ∆R = 0.2 around the electron and is required to be less than 3.5 GeV 1 . To
1 the calorimeter isolation of electrons is corrected for additional energy deposit from pile-up events and energy leakage into
the isolation cone.
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(b)