[Sane-analysis] Calculating d2

[O. A. Rondon]

I have updated the draft about the d2 method. New version here:
https://userweb.jlab.org/~rondon/analysis/asym/world/A2p-v4.pdf

Mark's question about fit choice led me to spot a typo on the
1/sqrt(Q^2) b1 parameter shown for the 1/W fit. The parameter is b1 =
-0.0423, not +0.432, which makes lots more sense.

Also, I have posted some illustrative plots of the 1/W fit, vs W and vs
Q^2. In each case the fit is calculated at the data's W, Q^2 for each
subset (SANE 4.7, 5.9, etc.), and at constant values of the variable not
 used as abscissa.
https://userweb.jlab.org/~rondon/analysis/asym/world/A2_data-fits.pdf

It can be seen that the W dependence dominates, as expected, from the
larger a1 factor in front of 1/W versus the b1 factor in front of 1/Q,
for comparable W and Q^2 ranges. I think this may answer in part
Mark's request about what data contribute at each Q^2.

I have also posted the spreadsheets I use to get the numbers and make
the plots. They are a bit big, but the main contents related to d2 is in
the tabs that open when the files are first loaded. Look for the latest
OpenOffice *.ods files in the same folder as the d2 draft
https://userweb.jlab.org/~rondon/analysis/asym/world/

I think it was clear in the end, but when I mentioned during the meeting
that the g1 twist expansion only involves even twist, I meant that the
OPE expansion of g1 involves only twist-2 matrix elements of even spin
(a0, a2, etc.) but only a0 is dynamic twist. The rest are TMC's. The
same goes for g2 and the higher spin d_i's.

Cheers,

Oscar