As stated previously, the only global alignment requirement of the muon
identification system is an alignment relative to the interaction
point.
The multiple scattering in the absorber material in front of
the muon tracking stations limits the angular resolution of
a 10 GeV/c track at the vertex to approximately 3 mRad or more. If
this error is projected from the first tracking station to the
muon-ID, the position resolution is approximately (5.4 meters)*
3x10
= 1.6 cm. An additional 1-2 mm of error occurs
at each of the absorber layers in the muon-ID detector.
Therefore, the muon-ID planes must not need to be aligned to
the vertex to better than approximately +/- 4 mm in the x and y
directions in order to have
alignment errors be negligible compared to multiple scattering
errors. The necessary alignment of the muon ID planes to the
vertex in z is outside the physical bounds of the space for
the muon identifier. Therefore, it is only required that the
z positions be measured after they are put in place, and this
measurement only has to known to within a few centimeters
relative to the vertex.