[Clascomment] OPT-IN: Resolving the proton form factor problem by comparing electron and positron scattering from the proton

[Larry Weinstein]

Dear Reinhard,

Thank you very much for your comments.  We will modify the title as 
several people suggested.

Reinhard Schumacher wrote:
> Hello TPE folks,
>
> I'm glad you are about to send this important result off for
> publication.  It looks like lots of people have pointed out the typos,
> so I'll skip those.  I just have a few style and content comments for
> you to consider.
>
> Abstract: The sentence "The cross section ratio increases with
> descreasing epsilon..." is a little confusing on first reading because
> we usually say what happens to a correlation with INcreasing value of
> the independent variable.  Also, for the naive reader it might help to
> say implicitly what the ratio was expected to be.  I suggest the
> rewrite: "The cross section ratio increases ABOVE UNITY for smaller
> values of epsilon at..."
added 'above unity'
> (Page and line numbers for November 14 draft)
> Page 2 line 38+: Here you discuss the TPECal to measure the "energy
> distributions of the ... lepton beams".  This made me ask myself, OK,
> what does that energy distribution look like?  You don't specify that
> in the paper.  I suggest you put in a line stating "The teritary beams
> had a momentum spread of XX% centered near YY GeV..." or something
> like that.
We now write: "The energy distribution rises rapidly from about 0.5 GeV 
to a peak at about 0.85 GeV and then decreases."
>
> Page 2 line 49: You are slipping into the jargon of the experiment
> here.  It would be clearer if you say "... the CLAS torus magnet and
> BEAM chicane magnet currents were ... reversed..."
We added 'beam' before chicane in a few places.
>
> General question that the paper does not address: despite listing a
> large number of corrections and systematic studies, nowhere do you
> mention positron annihilation.  How small an effect is that, and how
> do you know it?
It is significantly less than 0.1%.  We estimated it from the cross 
section and the material traversed by the positrons.
>
> Page 3 line 38: Here again you mention the beam energy distributions,
> but the paper does not indicate what that distribution is.  I think
> you ought to have at least a sentence about that.
see above
>
> Page 3 line 43+: Here you mention discarding some data for reasons
> that are not made clear in the paper.  I think this is a huge "red
> flag" in the paper in the mind of a reader.  Other CLAS commentators
> have pointed this out as well.  We discard data all the time when we
> do experiments.  As long as we are confident we are doing it for
> legitimate reasons, I don't think we need to burden the reader with
> such details.  My recommendation is to remove mention of this in the
> PRL paper.
We agree.
>
> Finally, I noticed Charles Hyde suggested a different title for the
> paper since this work is not entirely definitive and it does not solve
> all problems.  He has a point, I think, but if you change the title
> you might consider saying "TOWARD resolving the proton..."
Towards a resolution of the proton form factor problem: comparing
electron and positron scattering
>
> That's all.  Hope we beat the competition into print.
>
> Reinhard

-- 
				Sincerely,
				Larry

-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
weinstein at odu.edu
http://www.lions.odu.edu/~lweinste/