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

Chapter 4: Data Collection and Event Reconstruction 136
are removed from the two track lists, and the procedure repeated until no more
combinations are possible.
Note that, since the muon spectrometer covers the region |η| < 2.7 and the inner
detector coverage extends only up to |η| < 2.5, not all spectrometer tracks can be
matched to an inner detector track.
The results presented in this thesis use muons reconstructed with the Staco algo-
rithm, unless otherwise stated.
Inner detector based muon tagging
Tagging of inner detector tracks as muon tracks is an inside-out approach. There
are some muons that have well-measured tracks in the inner detector, but only isolated
segments in the spectrometer. This can happen for two reasons. Very low-pT muons,
after they have traversed the calorimetry, may not have enough energy to traverse
multiple spectrometer stations and may leave hits in the inner station only. Also,
energetic muons that pass through acceptance gaps in the spectrometer (e.g., at
η ≈ 0) fail to be reconstructed by the outside-in approach.
The muon tagging algorithms propagate inner detector tracks to the inner muon
stations and look for nearby segments. The Moore and Muonboy family algorithms
that implement this scheme are known respectively as MuGirl and MuTag.
MuGirl
For all extrapolated inner detector tracks above ≈ 3 GeV, MuGirl tries to form
segments in the muon spectrometer using a Hough transform-based pattern recogni-