(January 18, 2012) NOTE: From this update until my December 31 update I incorrectly calculated the background-asymmetry systematic. I have subsequently changed my methodology. Instead of taking the largest asymmetry from among the bins, I take the largest average of the two bins surrounding the pion peak (turns out to be the yellow beam). This is ~2%. The sizes of the resulting systematics are quite comparable to what has been reported.

One suggestion during the meeting on Wednesday was to plot the various asymmetry calculations on a common axis. This is, indeed, a very useful way to evaluate the various systematic effects; and thanks to all for the valuable discussion and feedback.

Figure 1: A_N vs. x_F

Plotted are the central values and statistical uncertainties for the various asymmetry extractions used for estimating systematics in the previous entries. One can see that in nearly all cases the mass window systematic differs most from the other calculations. 

Figure 2: A_N vs. p_T

Again, one sees that changing the mass window tends to have the largest effect on the central values. While this is somewhat unexpected it is very good to discover this and understand it before we move too far toward publication. It was discussed that perhaps one way to proceed is to employ a symmetric mass window and perhaps average the values to find the central values. Which such variation it is difficult to conclude which mass window is best as they should return the same value. I will evaluate another choice of mass window in the next update.