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User name D. Lhuillier
Log entry time 00:22:37 on October17,2005
Entry number 157174
keyword=Conclusion of quad scan
In left arm det2 is the horizontal segment. It corresponds to the high momentum and low Q2 part of the acceptance so one would expect higher rate in that segment.
The actual rate measured in det2 is ~4 times smaller than in det1 because the detector segmentation is not centered w.r.t. to the event distribution in focal plane (see Robert's entry 156948).
Tentative conclusion of quad scan (see Sarah's entry 157169):
*Det2 is sensitive to the quad settings. We observe variations in rate up to 20% for a 5 or 10% change in the quad settings.
*Det1 is much less sensitive.
*Despite the non-negligible rate change in det2 the combined detector width couldn't be reduced by more than 1%.
*Scanner runs seem to show that the elastic line is made broader when the quads are off nominal setting. Not obvious to see if the whole distribution is shifted or not. We couldn't run the macro for accurate comparison between two runs because of software problems.
I think that the observed different sensitivities of det1 and det2 are similar to what we see for the dithering slopes. The quad tweaking slightly moves the event distribution and the relative rate change is always bigger in det2. But most of the elastic events stay in the acceptance and the overall gain is negligible. Same thing happen with the dithering slopes, quite large for det2 and a lot smaller when averaged on both segments.