User name R. Michaels
Log entry time 15:28:30 on June 6,2008
Entry number 241297
keyword=Qasy for recent runsI was asked if helicity is ok. The best way I know to check is
to measure a clear asymmetry, e.g. Moller. One can also do a
sign check whereby a large charge asymmetry (Qasy) is induced
and measured in Moller and HRS, etc.
If Qasy were zero it wouldn't mean much, but if it is non-zero it
probably (?!) means there is a good helicity signal. In recent
runs Qasy is 500 to 750 ppm and about 3 to 4.5 standard deviations
from zero, e.g. run 1925, see fig 1.
Note, this uses "qasy_tst" in ~adaq/qasy. I used that because u10
BCM appears to be broken, so "qasy_tst" uses u1 instead.
Another thing to look for: Look at the digital helicity (in TS1
crate) versus the ADC helicity (in a Fastbus crate).
If these are in synch it is very unlikely there is a synch
problem with the helicity data. Check it !
FIGURE 1
