[d2n-analysis-talk] Request from Jin: Helicity Sign Check from 3He elastic runs

[Diana Parno]

Hello folks,

Jin has asked whether we're at a point where we can reasonably quickly  
determine an asymmetry in the LHRS elastic 3He runs. The specifics are  
below.

Looking at our list of special runs, it appears that the relevant runs  
were taken Feb 9-10 (runs 1203-1227). The half-wave plate was removed  
halfway through the run period, which makes for a nice check.

A Moller measurement was finished about six hours before the elastic  
runs began. That measurement gives a negative sign, which means that  
(if Moller and LHRS agree) we would expect a negative LHRS asymmetry  
for Runs 1203-1215 and a positive asymmetry for Runs 1215-1227.

Are we far enough on the LHRS calibrations that we can make this  
measurement? If the asymmetry is small compared to our uncertainty, we  
might not be able to trust the sign, but it would still be interesting  
to look at.

Best,
Diana

>
On May 3, 2010, at 1:31 PM, Jin Huang wrote:

> I am wondering whether you guys have "calibration" of sign of beam
> helicity.
> Say, when Moller polarimetry show a "+" sign, whether HRS see
> helicity=+1
> electron beam @ adchel_L.helicity=+1 or otherwise. Inserting or
> removing
> IHWP will flip the relation. However, sign of Moller and HRS is always
> correlated.
>
> The sign is important for any asymmetry involved with beam helicity.
> It's
> convention could be checked by analyzing sign of elastic he3
> asymmetry (not
> necessary analyzing amplitude, which take much more effort), whose
> sign is
> known.
>
> Will you be able to get the sign quickly? Thanks,
>
> Jin
>