Hi BLASTers,
Here are some results from the data taken over last weekend.
1. Timing issues.
You might remember that it was my strong opinion that timing
is way off (up to 10 ns) for retiming signals from different paddles.
Well, last data show much better timing. most of the paddles are timed
within 1-3 ns, and none looks worse than 5 ns. That is a good side of
the story. The bad part is that nothing has been changed since my last
analysis, and it is unclear why the situation has suddenly improved.
Also, I've noted some instability. For instance, "retiming" time
jumped between two different peaks for the paddle L11 during runs 1255-1258.
The amplitude of the jump was about 2 ns. I also noted smaller "drifts"
in retiming time (.2-.5 ns) from run to run in some other channels.
Most suspicious unit in all cases is a meantimer.
2. B-field and phototubes.
It is rather ineffective way to investigate this dependence (IMO, it
should be done with a flasher, when we manage to bring it's amplitude down
to acceptable level), but for whatever it worth, I see about 10 % reduction
in the signals with B on (I=3500 A). Accuracy and reliability of this
conclusion are rather low.
3. Left-Right asymmetry in elastic events.
After analysis, I came to a solid conclusion that the efficiency of
our detectors for electrons is low due to high thresholds (or low voltages,
whatever). It is low, and it is different for different paddles. That explains
the observed asymmetry.
Genya
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