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Beam-Beam counters

From a physics point of view, there are no stringent positioning requirements placed on the BB counters. All they need to do is catch the fastest particles near the detector axis. This task is to first order independent of (small) shifts in the plane transverse to the axis. Timing shifts due to repositioning errors along the axis are only 3.3 ps/mm. Thus the BB counters can tolerate many mm of error before their performance is affected. Since the expected placement accuracy is at the sub-mm level, the physics do not place additional requirements on the alignment.



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Christine Jarmer
Tue Jul 25 14:56:49 MDT 1995