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

Chapter 6: Event Selection 180
6.2.4 Estimation of efficiency scale factors
Trigger efficiency for single muons
Since we require the L1_MU6 trigger in our analysis, we must estimate the efficiency
of this trigger, for single muons and for Z → µµ events. We first note that, since
the trigger technologies are different in the barrel and the endcap regions, we must
measure the single muon trigger efficiency separately in each. The event selection for
this purpose must be independent of any muon trigger so as not to bias the sample.
We perform the study on the same initial dataset as used in the cross-section
analysis, using events that are in the Z → µµ good runs list. We require the same
primary vertex and high-pT event selection as in the analysis, with the exception that
the combined muon pT is required to be greater than 20 GeV instead of 15 GeV.
Events must pass the L1_J15 trigger, which requires a jet with ET > 15 GeV, and is
independent of any muon trigger. In applying the |z0 − zvtx| cut on the muon, we use
the primary vertex that has the largest ΣpT and satisfies the vertex selection criteria.
Table 6.5 [62] summarizes the event selection criteria.
Event selection
Primary vertex Nvtx ≥ 1 with Ntracks ≥ 3
|zvtx| < 150 mm
Trigger L1 J15
Muon selection
Muon type combined muons
pT > 20 GeV, |η| < 2.4
Muon quality pMS T
|pMS T
> 10 GeV
− p ID
T | < 15 GeV
|z0 − zvtx| < 10 mm
Table 6.5: Event and muon selection criteria for single muon trigger efficiency
measurement.