User name A. Deur
Log entry time 17:10:53 on July 6,2001
Entry number 65641
Followups:
keyword=a helicity checkHere the plot of the "cosmic asymmetry" for 12 runs belonging to the last period of data taking (longitudinal, beam 1/2 wave plate in, target 1/2 wave plate is out).
By "cosmic asymmetry" I mean the number of cosmic recorded for each helicity state of the beam. It is not corrected for charge asymmetry (and should not). If there is no problem with the helicity signal, we expect a zero asymmetry.
To select cosmic events, I am just doing a cut on the number of track (I am choosing the 0 track events. Of course, there is still some event coming from the target (so they are able to produce an asymmetry) among the 0 track events. However, the amount of target event should be well below 1%. At worst, their raw asymmetry will be about 2% (from Xiaochao analysis of the pions for the longitudinal target) so the correction for that is should be much less than 0.0002. Good enough for now (later one may want to do more than a 0 track event cut)
The asymmetry for both arms are compatible with 0. The left arm is at one sigma. I don't know if this is due to the problem that Nilanga pointed out this morning.
FIGURE 1
