Chi,
What you are saying is very worrisome. Though, I agree that a holding
field fluctuates few degrees up and down, a shift of 12 degrees is
significant. I think that it is important in the light of this to
repair the hall probe inside of the scattering chamber.
Vitaliy
P.S. 20 degrees is very non optimal for medium and large Q^2
measurement of GeN. Low Q^2 is ok.
Chi Zhang wrote:
>Hi, Just for record.
>
>in the last two days of D2 running, spin angle seemed to have drifted
>to below 30 degrees. in fact could be very close to 20 degrees judging
>from ed elastic asymmetries. the sympton is that asymmetries in Parallel
>kinematics almost vanish.
>
>I am afraid this is less than optimal for Pzz measurement, T20 and maybe
>Gen.
>
>To Shift takers: when running ed_xs.C, you can specify the spin angle by:
>root ed_xs.C #### #### spinthd=<value>. theory curves for 20, 30, 32, 35,
>37, 40, 45, 47, 48, 50 degrees are built in.
>
>Chi
>
>
>
>
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