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

compatible with a constant within the statistical uncertainty.
acceptance [%]
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
ATLAS Internal
2ID + TL
w/o pileup reweighting
w/ pileup reweighting
0
0 5 10 15 20
Figure 5.14: Acceptance as a function of the mean number of interactions per bunch crossing (〈µ〉). The
black dots are raw MC events and the magenta stars are MC events after pile-up reweighting (they show
the region of 〈µ〉 relevant for the data used in this analysis).
5.6.2 3ID Analysis
The additional, orthogonal, channel used in the combined result to be presented in Chapter 8 corresponds
to that where three fully reconstructed leptons (electron, muons) are selected. As mentioned above, this
part of the analysis was performed by a different group in the collaboration. However it is explained here
for completeness and clarity of the final result, which combines the two channels.
The 3ID selection is very similar to that of the 2ID+TL. The main difference, which ensures orthogo-
nality, is that instead of requiring exactly two ID leptons and one TL, three ID leptons are required, with
the leading lepton having pT > 25 GeV. In the 2ID+TL selection this is automatically ensured by the
pT > 25 GeV cut used in the TL selection. Also, no b-tagging requirement is used in this analysis.
In the initial selection events are required to pass one of the single leptons triggers, and to include at
least one good primary vertex. Events which contain any jet with pT > 20 GeV that fails the jet cleaning
requirements [102] are rejected. Events with noise bursts in the LAr calorimeter or with cosmic rays are
discarded. Events with exactly three ID leptons are selected, provided the three leptons are matched to
the same primary vertex. At least one of the reconstructed leptons has to match a trigger lepton. The
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< µ >