Here is the message I tried to send out yesterday, that I referred to in the analysis meeting. You can find the plots in
/usr/local/www/html/PRIVATE_RESULTS/USEFUL/ANALYSIS_MEETINGS/meeting_050720
As a summary, here is a todo list to get to the bottom of the kinmatic offsets:
- switch sectors in geometry file
- hand integration of track offsets
- fit middle wch chamber geometry
- global fit to geometry from staight tracks, cosmics
--Chris
It was suggested at the collaboration meeting to test the difference in
momentum offsets between the currently used fieldmap (mostly
Biot-Savart) and the corrected one (fieldmap during commissioning) using
Monte Carlo.
Here the results of that study, the change in momentum offsets (p-p(th))
in going from the corrected fieldmap back to the old one. These are
shown for the electron and proton in each sector as a function of the
track angles (z=0). Note that white is the underflow color and red is
the over-flow for the scale shown. These offsets are integrated in phi
over the yield to compare the offsets shown in slides #4 and #5 of my
presentation at the collaboration meeting.
http://blast02.lns.mit.edu/PRIVATE_RESULTS/USEFUL/ANALYSIS_MEETINGS/meeting_050713/Crawford_fieldvar_July15.ppt
--Chris
PS: One thing to note, it appears there is a large difference between
the fields in the right sector at 33-38 degrees, but only in the
horizontal plane. It probably corresponds to peak at ~ x=-80, z=110 cm
in the plot of the difference in the fields in slide #3. all of the
field comparisons were made in the y=0 plane where this anomaly is, but
when you average over phi, the average offset is much less. also note
that the extraction of the fieldmap from the offsets (slide #19) also
shows a bump of the same size close to the same position.
In conclusion, I am still fairly confident that the offsets are due to
geometry (or something else) rather than the magnetic fieldmap.
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