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

Chapter 6: Event Selection 200
Figure 6.19: pT distribution of Z decay muons in Monte Carlo without smearing
(points) and with additional smearing (line).
6.2.6 Isolation cut efficiency for Z → µµ events
We study the efficiency of the isolation cut on Z decay muons using a tag-probe
approach similar to that used to determine muon reconstruction efficiency. The event
selection criteria are the same as for the reconstruction efficiency study (Table 4.6).
The tag is selected to be a high-pT isolated combined muon, while the probe is
required to be a high-pT combined muon without any isolation requirement. The
invariant mass of the tag and the probe must be in a 10 GeV window around the Z
mass. The selection criteria for events, tags and probes are summarized in Table 6.14.
In determining the isolation cut efficiency, we must take into account the fact that
either of the two muons from a Z decay can pass the isolation cut. We want to define
the efficiency such that for an event in which the probe passes the isolation cut, both
the tag and the probe contribute to both the numerator and the denominator of the