Measurement of the Z boson cross-section in - Harvard University ...

Chapter 6: Event Selection 171
Entries
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1
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∫L
dt = 331 nb
Data 2010 (
Z → µ µ
bb cc
W → µ ν
Z → τ
tt
s=7
TeV)
0 5 10 15 20
SCT hits/track
Entries
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Data 2010 (
Z → µ µ
bb
cc
W → µ ν
Z → τ
tt
-1
∫L
dt = 331 nb
s=7
TeV)
0
0 10 20 30 40 50
TRT hits/track
Figure 6.6: SCT hits (left) and TRT hits (right) on inner detector tracks matched to
muon spectrometer tracks for signal Monte Carlo, background Monte Carlo and data
after event preselection. The total Monte Carlo event number has been normalized
to the number of events in data.
Kinematic distributions
Figure 6.7 shows muon kinematic distributions (pT , η and φ) at the preselec-
tion stage. Figure 6.8 (left) shows the track isolation ratio versus muon pT , while
Figure 6.8 (right) shows the dimuon invariant mass distribution. The Monte Carlo
predictions in these figures have been normalized to the number of data events. As
expected, QCD backgrounds dominate the sample owing to their large cross-sections.
The data and Monte Carlo show reasonably good agreement within the statistical
uncertainty.
6.2 Z signal acceptance and efficiencies
The Z → µµ production cross-section is given by: