Muon Alignment Ken Read, Donny Hornback, David Silvermyr, Vince Cianciolo

Mea Culpa Last year, when Melynda saw effects that looked like scale errors (dx α x) I checked the MUID locations with a tape measure and verified the survey locations to w/i ~1cm. It never occurred to me that the survey numbers were never loaded into the database. They weren’t, and the numbers in the database have significant errors in z (up to 9 cm). –x and y are OK.

Consequences I can imagine that this could effect the determination of panel efficiencies. I can also imagine that it would effect the overall MUID reconstruction efficiency. –We can test this by rerunning the muid efficiency analysis with the MUID survey numbers included. It will modify the LL1 symset maps. Care will be needed to incorporate these changes in a self-consistent manner for all data pre-Run7. –For instance, efficiency calculations should have the response function use the new #’s (since the tubes were in the correct location), but the reconstruction code should use the old #’s since that’s what the data were reconstructed with.

Does this solve the W problem? David re-passed the run-5 J/Ψ tracks w/ various attempts at alignment corrections –Melynda’s MuTR + MuID (black) –Catherine’s MuTR + MuID (yellow) –Min Jung’s MuTR only (blue) –Corrections based on MuID survey + Melynda’s MuTR corrections (green) –MuID survey corrections applied backwards + Melynda’s MuTR corrections (red) DG0 vs. R is plotted for high momentum tracks under the different correction schemes. Significant improvement w.r.t. corrections by Min Jung and Catherine (which had limited or no MuID corrections). Modest improvement w.r.t. Melynda’s corrections. Serious degradation when MuID survey corrections are applied backwards. W/ correct survey #’s DG0 is flat vs. R, but is still relatively large. No improvement in DG0 below R~250 cm.

Follow up Ken is discussing with Ed O. the possibility of a partial re-survey to verify the survey numbers. –Although since x and y locations are all within a few millimeters of expectations we suspect that they are fine. Chun and Sotiria are verifying the length of the hanging rods which are used to determine locations of lower panels. When I discussed w/ Walter the other day he wondered about our assumption of B=0 during field-off running. –He pointed out that the “donuts” on the South magnet return yoke had to be pried off (!) during the installation of the MuID collar.