Meeting minutes:
Present at the meeting: M. Ito, D. Lawrence, E. Clinton, M. Payen, A.
Teymurazyan, R. Demirchyan, D. McNulty, Y. Prok, E. Pasyuk
On the telephone: D. Dale, A. Bernstein, L. Gan, A. Gasparian
1) Review of last week's minutes: Marvin Payen provided the PRIMEX poster
for the Open House on April 16th (thanks, Marvin!), and Dave Lawrence did
the liquid nitrogen demonstration at the same event, with no reported injures
to anyone (good job, Dave!)
2) Dustin presented an update on his pi-zero analysis. His slides can be
found at
http://www.jlab.org/primex/weekly_meetings/weekly_2005_04_22.html
Some of the shown distributions included the test of elasticity
"(e1+e2)/ebeam" which is centered at ~1.1. Eugene mentioned that we
need to incorporate the tagger energy correction from g10 run, but it
will be a small correction, on the order of a few tenth of a percent.
Dustin also presented his method of subtracting the background under the
elastic pion peak. Eugene suggested trying to subtract the sideband not
only on the lower energy side, but also one on the higher energy end.
This procedure would give a better constraint on the scaling factor for
the background subtraction.
3) Aram and Dave discussed the problem of the
scaler "anomaly", in which, "live1" and "live2"
(gated and ungated scalers, correspondingly, driven by the 200
KHz clock, internal to the trigger supervisor), are observed in some
events to have values smaller than the ones in the previous events,
which should not happen. The conclusion of this discussion was that the
problem is caused by the least significant bit at the byte boundary
flipping prematurely. This hardware problem does not seem to occur
in both scalers simultaneously in the same event, which makes it easier
to fix in software by cross referencing.