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

Chapter 4: Data Collection and Event Reconstruction 151
Because the tag and probe tracks are required to be largely back-to-back in the
azimuthal coordinate, the tag-probe method can miss φ-symmetric inefficiencies in
the detector. This effect can lead to an overestimation of the overall efficiency. The
correct way to determine the efficiency is to compute it as a function of φ which,
however, requires much larger statistics than we use for this analysis. Nevertheless,
we obtain a crude estimate of this effect by measuring the efficiency with probes for
which (∆φ)TP