[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 your considerations.
Yes, what you suggest is another option. But that produces a single curve,
which does not give any indication of the variations in energy that are
inherent to the way the PWA prediction is constructed. For that reason, we
regard the form of the presentation in figure 4 to be more useful.
Andy




On 3/15/17, 5:23 PM, "Eugene Pasyuk" <pasyuk at jlab.org> wrote:

> Concerning SAID band. Another option of presentation could be cross section
> weighted average over a bin. The experimental data points are exactly this.
> 
> -Eugene
> 
> ----- Original Message -----
>> From: "Andrew Sandorfi" <sandorfi at jlab.org>
>> To: "Eugene Pasyuk" <pasyuk at jlab.org>, "clasmbr" <clasmbr at jlab.org>,
>> "clascomment" <clascomment at jlab.org>, "Daniel
>> Carman" <carman at jlab.org>, "Michael Dugger" <dugger at jlab.org>, "Kyungseon
>> Joo" <kjoo at phys.uconn.edu>, "Alexandre Deur"
>> <deurpam at jlab.org>, "Patrick Collins" <pcollins at jlab.org>, "Charles Hanretty"
>> <charleshanretty at gmail.com>, "Tsuneo
>> Kageya" <kageya at jlab.org>, "Annalisa D'Angelo"
>> <annalisa.dangelo at roma2.infn.it>, daoh at jlab.org, jamief at jlab.org,
>> cbass at jlab.org, "Peng Peng" <pp9e at virginia.edu>
>> Sent: Wednesday, March 15, 2017 7:13:53 PM
>> Subject: Re: comments on  The Beam-Target E asymmetry for vec gamma vec n ->
>> pi- p in the Nâ resonance region
> 
>> 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
>> ________________
>> Done
>> ________________
>> 
>> 
>>> 
>>> page 2, column 1:  in "Here we report...." I would move equation "of E=..."
>>> right after "... double polarization measurements..."
>> ________________
>> Done
>> ________________
>> 
>> 
>>> 
>>> page 2, column 2: "...retains about 25% more events..." more compared to
>>> what?
>> ________________
>> Compared with the Bksub procedure, with which it is contrasted in the
>> beginning of that paragraph.
>> ________________
>> 
>> 
>>> 
>>> page 3 : in two places where you talk about extrapolation to P_miss=0 use
>>> "systematic uncertainty" instead of "systematic error"
>> ________________
>> Done
>> ________________
>>> 
>>> 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.
>> ________________
>> 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.
>> ________________
>> 
>> 
>>> 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.
>> ________________
>> 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.
>> ________________