[b1_ana] [Fwd: Re: PR12-13-011]

[J. P. Chen]

Hi, Oscar,

We have done this for the transversity experiment where
our main goal is single target spin asymmetry (beam unpolarized)
and our secondary goal is to get double spin asymmetry as well.
So the beam polarization was high (typically 80%).
We do have beam helicity information in the data such that we can
have the buckets count exactly equal between two beam helicity states.
Due to the parity beam feed back system, we got the charge asymmetry
between the two states to be at 10-5 level (<50 ppm), much better
than we need. (Without the feedback system, we can typically only control
the charge asymmetry to ~1x10^-3.) For transversity, the systematics
due to false asymmetry from beam not totally unpolarized is completely 
negligible.

For our low current running with polarized proton/deutron target, we 
will need to
rely on feedback system to be run from the other hall. As in g2p case, 
we rely on
QWeak feedback, which provided charge asymmetry in Hall A at the 10^-4
level.

Karl and I can get our g2p students to provide some plots.

Cheers.

Jian-ping


On 5/14/2013 5:58 PM, O. A. Rondon wrote:
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