Slides 30-October-2002

• To understand what the issues are you need to understand what the crossing time has to do with our stub-finding. The third page in this set shows what we calculate for the time at which a particle crosses the BMU system. The first page in the set shows the difference between the crossing time as found by the BMU and the time of a BSU scintillator hit. When I demand that the two times agree, I find the plots on the fourth page. It is easy to see that the rear scintillator is more afflicted with halo particles which arrive early, and in the fifth page you see that most of these come from the West side.

  My algorithm selects the best hit collection based on whether or not the chi-squared is better than that of an overlapping hit collection. It is easy to see that unless you correct for the crossing time the results may be wrong. You can see the original algorithm's chi-squared here, where the difference between the upper plots is that the left one is for stubs that crossed stacks and the right for stubs within a single stack. For Bob's algorithm the chi-squared plots look very different: All in the upper left, 3-hit stubs in upper right, 4-hit in the same stack in the lower left and 4-hit crossing stacks in the lower right.

  It is perfectly plain that there are some alignment issues that needed to be dealt with here.

• After making the adjustments to hit positions for the crossing times (these adjustments are made internally, and do not change the hit collections), I found the chi-squared numbers still did not make sense. I added some kludge terms to the timing corrections, which were different for stubs going through a single stack and stubs crossing stacks, and adjusted these until the chi-squared was a minimum. I regard this as a temporary hack that should last only until I can find out the origin of the misalignments. I don't expect the results to change when I find the underlying problem, of course.
• Both stub-finders wind up with a deficit of CdfMuons in the rear South West side. Both find essentially the same number of CdfMuons.

Modified 30-Oct-2002 at 14:17

http://hep.physics.wisc.edu/~jnb/imu/30Oct2002

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