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

Chapter 6: Event Selection 175
Figure 6.9: Left: Comparison of the number of reconstructed vertices per event in
periods A-C with that in period D. Right: Comparison of the number of reconstructed
vertices per event in data and Monte Carlo. The distributions are from after the
muon pre-selection requirements. Vertices are required have |z| < 150 mm from the
nominal interaction point and at lest three inner detector tracks associated with it.
The data-taking periods were defined in Chapter 4.
is the corresponding fraction in Monte Carlo. We use vertices after the event pre-
selection that satisfy |zvtx| < 150 mm from the nominal interaction point and have
at least three associated inner detector tracks. The event weights used on the Monte
Carlo as well as the fraction of events with each vertex multiplicity are summarized
in Table 6.2. Further details of the weighting procedure can be found in [62].
6.2.2 Acceptance of Z selection from Monte Carlo cutflow
We can define the acceptance as the number of events passing our selection criteria
divided by the total number of generated events. Table 6.3 shows the number of Monte
Carlo Z → µµ events passing each step of the selection as well as the efficiency of
each step relative to the full sample and to the previous step.