Hi,
here are the minutes:
-News from the wire chamber calibration front
+Doug found and fixed two bugs in his code to analyze straight
tracks. After this, he sees offsets in the straight tracks for Aaron's
wire chamber calibration but none for his own. Concluded that Aaron's
calib was wrong.
+CVS, Wire.Cal and blast.geom were updated and MK recrunched the
December 2004 hydrogen data. Results have much improved, kinematic
corrections are much smaller
+momentum and angle of protons are almost consistent with each other
+momentum offset pe-pe(the) is sector-symmetric, finite offset in
Hprofile perhaps due to radiative effect
+still some offset in coplanarity, not understood
+still some offset in vertex, not understood
See also EG's and AS's plots in
http://blast.lns.mit.edu/PRIVATE_RESULTS/USEFUL/ANALYSIS_MEETINGS/meeting_060315/
Shifted angles, momenta, and z's will have impact on asymmetry
analyses, but also the yield-weighted average of the spin angle will
be different. CC will redetermine the average spin angle from ep
elastic asymmetries and from yield-averaging the spinangle map. As the z
distribution will be more centered, it is expected that the average spin
angle from the map increases.
MK will continue to recrunch data for deuterium from 2004 and
2005. CZ will update ed elastic analysis also in regard of spin angle
determination.
The spin angle will also be remapped soon. Hopefully the resulting
picture will be more consistent.
Timeline: At some point we have to define when we're happy and apply
residual corrections.
Constraints are: Collaboration meeting on April 7 (and analysis
meeting on April 5 or 6). Goal would be to discuss analysis updates on
this occasion. People need to be given adequate time to perform
analysis updates, i.e. recrunched data should be available at least
7-10 days before. The full recrunch will likely take ~1 week.
While I'm continuing to recrunch data under using the present
calibration, we give it a few more studies at this time before we draw
the line. Another goal of the April meeting would be to address and
agree on what exact additional steps are to be taken before the status
will be frozen for conferences and first papers.
Besides Dallas, the conference season starts in May ...
-p(e,e'npi+) event selection (Kelly Michaelsen, Dartmouth)
Kelly is showing us her study of event selection of above triple
coincidences. Analysis done from DST. Seems that there are
significantly more events of this type than in the FLR ntuple.
+Would be interesting to study n-detection efficiency by comparing the
p(e,e'npi+) yield with the p(e,e'pi+) yield, where the neutron was
expected to be within the acceptance (well, outside it's zero).
Regards,
Michael
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