[Clascomment] comments on The Beam-Target E asymmetry for vec gamma vec n -> pi- p in the Nâ resonance region

[Dr. A.M. Sandorfi]

Hi Eugene,
Thanks for the comments. My actions/responses are embedded below.
Andy




On 3/15/17, 3:48 PM, "Eugene Pasyuk" <pasyuk at jlab.org> wrote:

> Several comments.
> 
> page 2 Fig. 1 caption: replace distance -> position
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Done
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> 
> page 2, column 1:  in "Here we report...." I would move equation "of E=..."
> right after "... double polarization measurements..."
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Done
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> 
> page 2, column 2: "...retains about 25% more events..." more compared to what?
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Compared with the Bksub procedure, with which it is contrasted in the
beginning of that paragraph.
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> 
> page 3 : in two places where you talk about extrapolation to P_miss=0 use
> "systematic uncertainty" instead of "systematic error"
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Done
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> 
> Fig. 4. There is an inconsistency in how SAID and BnGa curves are presented.
> SAID curves go all the way to the extreme angles of 0 and 180 degrees while
> BnGa are truncated at experimental points. Perhaps it makes sense to truncate
> SAID the same way.
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The BnGa group provided their fitted expectation values for E only between
the angles of our data set. The SAID group provided the full range. I don't
see an advantage in showing less information. On the other hand, there is
one advantage in showing the full range for at least one of the two PWA,
namely to demonstrate that the curves indeed do go to +1 at the 0 and 180
deg limits as required by symmetry, even though the transition can be very
rapid at small angles.
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> Also showing SAID as a band is somewhat ambiguous. It is not obvious which
> side of the band correspond to the upper and lower edge of the bin.
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The side of the band corresponding to the upper or lower limits doesn't
really matter. (In fact, at some energies they cross over.) Recall how these
are generated. These curves are from an Energy-Dependent PWA, which is a
smooth fit to a set of Energy-Independent solutions. The latter are made by
binning the world's data in W and assigning all measurements within a
particular bin to the centroid energy of that bin, even though all those
data were not taken at exactly the same energy. So there is an inherent
energy uncertainty in this PWA process. Showing the spread of predictions
for the limits of our \pm 20 MeV bins is a way of indicating the approximate
effect of this PWA uncertainty.
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