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

Chapter 6: Event Selection 184
Figure 6.12: L1 MU6 trigger efficiency as a function of the azimuthal coordinate of
selected muons in the barrel (left) and in the endcap (right). The data efficiencies
are compared to those from W → µν Monte Carlo.
from the dependence on the muon reconstruction algorithm and the pT cut on the
combined muon. The Staco reconstruction chain requires at least one hit in trigger
chambers in both η and φ, which can bias the efficiency measurement. The Muid
chain does not have this requirement (Section 4.2.3), so that any possible bias can
be estimated by re-measuring the trigger efficiency using Muid muons and taking the
difference between the two measurements. We find this difference to be 1.38% in the
barrel and 0.92% in the endcap, which we take as a systematic.
We estimate the effect on the measurement of the pT cut on the combined muon.
By varying the pT cut by ±5 GeV around the nominal value of 20 GeV, we found
that the efficiency changed by 1.36% in the barrel and 0.46% in the endcap, which
we assign as a systematic.
Other sources of systematic uncertainty include the value of the |p ID
T − p MS
T | cut,
the muon-RoI matching criteria, the size of the search range in RoI-finding and the
dependence on the muon η distribution 3 . The various contributions to the systematic
3 The muons used in this efficiency measurement are predominantly from heavy-flavor decays,
which can have a different η distribution from W/Z decay muons. This can result in the trigger