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

Chapter 4: Data Collection and Event Reconstruction 146
Track type Tagged InDet tracks Combined muons
Prompt muon fraction 0.793 ± 0.003 0.830 ± 0.003
Table 4.3: Prompt muon fractions in data samples extracted using template fitting
with Monte Carlo templates. Errors are statistical only.
Both the numerator and the denominator of the efficiency estimation are now
corrected using the prompt muon fractions. The resulting combined muon recon-
struction efficiency is found to be 0.994 ± 0.006(stat) in data and 0.986 in W → µν
Monte Carlo.
The systematic error on the efficiency is largely due to decay-in-flight contam-
ination. We estimate this error by comparing the result from the template fitting
with a second method in which the efficiency is computed as a product of two factors
without the decay-in-flight correction. The two factors are:
• the reconstruction efficiency of standalone muon tracks with respect to tagged
inner detector tracks
• the reconstruction efficiency of combined muon tracks with respect to the stan-
dalone tracks
The standalone muon track reconstruction efficiency is estimated as the fraction of
tagged inner detector tracks within a cone of ∆R 10 GeV, |p ID
T −
p MS
T | < 15 GeV, and ∆RID,MS < 0.1. This selection reduces the decay-in-flight
contamination in the sample, although it does not eliminate them. The fraction of
selected standalone tracks which are within a cone of ∆R