87.41 +/- 0.12 (stat) +/- 1.32 (sys) %
89.93 +/- 0.05 (stat) +/- 1.12 (sys) %
Mindy's HAPLOG post:
Final result: 87.41 +/- 0.12 (stat) +/- 1.32 (sys) % (??)
chi^2/NDoF = 1.09 for 13 points over the experiment
|Rel Uncer. (%)|
|Gain shift||1.3||email from Megan Friend, see below|
Systematic Error Notes
- From Megan over gain shift:
I don't think I'm going to be able to get a number for the gain shift during PREX, although it should scale linearly with signal-background size. Using the 1% gain shift we saw during HAPPEX (signal+bkg to background = 122e6 to 53e6), that would give us a 0.8% gain shift for PREX (signal+bkg to background = 48e6 to 30e6 at 1kHz * 3.3 to convert to 30Hz). This would give us a change in the final polarization number of 1.3%, if it's folded into the background subtraction ( which comes from comparing a background subtraction of (48e6-30e6*(1.008))/(48e6-30e6) ). So I'd say the possible gain shift gives you a 1.3% systematic error.
- From Megan over radiative correction:
I just ran through the PREX data to add in a radiative correction, and I get that this increases the analyzing power by 0.3% (from 0.01828903 to 0.01834393). This is consistent with what I've seen, so I think it's safe to add that in there.
There is an increase in analyzing power of 0.3%, which corresponds to a decrease in beam polarization by 0.3%. Therefore, the final analyzing power should multiply by (1+0.003) due to A_real = A_exp * (1+0.3%)
w/o the radiative correction:
analyzing power = 0.01824526 +- 0.00002583 (sta.)
w/ the radiative correction:
analyzing power = 0.018299996 +- 0.00002583 (sta.)
Final result weighted average: 89.93 +/- 0.05 (stat) +/- 1.12 (sys) %
(not sure if the systematic is relative or absolute)
Sasha's report at the Jan 2011 collaboration meeting
The radiative tail leads to an effective drop in the measured Q^2 by 0.68%
See Kiad's presentation
The acceptance for the first excited state of Pb is <0.1%. It's expected to have an asymmetry ~1.3 of the elastic asymmetry so it is totally negligable.
The first excited state of carbon is outside our acceptance and does not contribute