The Drift Tube system consists of 12 sectors per wheel, each having a length of
3 m and covering an angle 
of 30 degrees (in the r- plane). In
each of the 4 muon stations a sector covers the information of 12 drift-planes
arranged in 3 ``superlayers'' with 4 planes each. Two of the superlayers are
used to measure the 
coordinates, the third one can be used to measure
, but these data are not yet included in this analysis. The Drift Tubes
are equipped with a chamber trigger logic that uses a mean-timer technique to
identify also the bunch crossing from which the muons originate (Bunch and Time
Identifier BTI). Each
track crossing a superlayer gives a track-segment with a given position, angle
and ``quality'' (depending on the number of planes used). The track pairs
from the inner and outer superlayers per station are combined by the Track
Correlator (see [1]). Using the position and angle information
of one track segment, the Muon Track Finder (MTF) [5] extrapolates it to
the next muon station and checks if any of the track-segments found there
fulfil a certain matching criterion to form a track.
After successful extrapolations and the use of ``quality'' criteria to get rid
of ghosts and probably bad tracks one gets the track parameters. Either a
bending angle or the difference of the azimuthal angles of two stations is
used via lookup tables to assign 
to a track. is evaluated from the
wheel position and from the Track Correlator. The lookup tables used
have been created by using 1000 muons of fixed inside a wheel with a flat
distribution. The mean value of the difference between the azimuthal
angles of the hits in two stations will then constitute the functional
relation for the assignment. The final selection of the 4 muons with the
highest (per ring) follows the process of extrapolation, track finding
and assignment. The assigned values for and are given on a
nonlinear scale still under discussion, as well as the size and definition of
the ``quality'' variable. At the moment 10 values in (0., 0.19, 0.23,
0.28, 0.42, 0.56, 0.66, 0.76, 0.88, 0.98) and 28 values in are foreseen
(2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 10, 12, 14, 17, 20, 25, 30, 35, 40, 50, 60,
70, 80, 100, 120, 140, 170, 200, 250 GeV/c). Only tracks found consistently
in at least two muon stations are regarded as reconstructed.
