[Clascomment] OPT-IN: Separated Structure Functions for Exclusive K+ Lambda and K+ Sigma 0 Electroproduction at 5.5 GeV with CLAS

[Reinhard Schumacher]

                                                     11-12-12

Hello Dan, Kijun, and Brian,

I have read your draft paper "Separated Structure Functions...with
CLAS".  You have done a very thorough job in presenting your analysis
work.  I have the following questions and comments about the draft
paper.

page 2 second paragraph: I would delete this paragraph.  It is too
general and broad, and does not pertain directly to anything in your
results.

page 2, fourth line from bottom: "have employed PARTIAL WAVE fits
from..."

page 3 line 3:  a mistake here:  the ELSA accelerator IS at Bonn, so
you don't want to mention it twice.

page 3, second paragraph: your sequence of observables is a little
odd.  Why not mention cross sections first?

page 4, line 11: please add the reference to the CLAS beam-recoil
polarization data:

%\cite{Bradford:2006ba}
\bibitem{Bradford:2006ba} 
  R.~K.~Bradford {\it et al.}  [CLAS Collaboration],
  ``First measurement of beam-recoil observables C(x) and C(z) in hyperon photoproduction,''
  Phys.\ Rev.\ C {\bf 75}, 035205 (2007)
  [nucl-ex/0611034].
  %%CITATION = NUCL-EX/0611034;%%


Page 4, paragraph 4: "The findings..."  This sentence is content-free,
i.e. without helpful information.  Try to remove it and add the
reference to a better spot in the text.


page 5, lines 4 to 7: this sentence has a grammatical issue: the first
and second parts of it don't match.  I'm not sure what you wanted to
say.

page 5 second bullet:  "parametrization" is the standard spelling 

page 6 7 lines from bottom: I don't think you need to say explicitly
that we are working in the one-photon exchange approximation.

page 10, Eq (5):  you have an extraneous "=" sign at the  beginning. 

page 11 Eq (6):  you neglect to tell the reader what \sigma_0 is.

page 11 after Eq (7), you mention P_b but you don't actually use it
anywhere.

page 12 bottom:  The paragraph that begins on this line would be
better placed prior to the preceding paragraph (except the last
time).  If you do that the information will be presented in a better
order, I think.

page 14, Eq (9):  you never define what you mean by \delta\eta, even
later in the paper.  You can probably get rid of this whole equation:
it adds nothing to the paper.

page 14, Section B. and beyond: this whole section suffers from a case
of TMI: "too much information".  It is all standard stuff that has
been written about before, and adds nothing toward making your
results convincing.  Can you shorten this a lot, perhaps by referring
the reader to the identical steps taken in previous work, such as Ref
[15]?

Page 15 Fig 3:  I can't see the K+ band AT ALL on this plot.  You need
a better figure.

Page 15 Fig 4: This looks awful!  Why are you showing the missing mass
spectrum at this early stage of the analysis?  If I read your text
correctly, this Figure is before you reject bad particle ID on an
event basis (kaons that are really pions, etc).  I am sure e1f data
can be cleaned up a lot from this point to make a much more impressive
plot.  Am I missing something?

page 16 Fig 5: replace 'extents' with 'domain'

page 17, Fig 6: delete the little statistics boxes at the top: they
are unreadable and uninterpretable to the average reader

page 18 Fig 7: this is another example of TMI.  I don't think this
figure helps make your case.

page 19 para 2, line 6 "tuned"?? What do you mean by this word?  State
explicitly what you did.  Also, this sentence is repeated almost
verbatim at the end of the next paragraph.

page 20 Section 2.  again, a case of probable TMI.  This all gets
rather tedious, and I am not sure you did anything new or different
than what has been done in a dozen other CLAS analyses.  If that is
the case, you can shorten this a lot.

page 25 below the middle:  "...was combined linearly with that
portion..."  What do you mean by this?  Did you just add the
uncertainties, and if you did, why is that legitimate?

page 26 Fig 11:  This figure would look more impressive if you
suppressed the zero in many of the panels.  It might be worth doing
that for the visual impact.  

Fig 13, 14, 15, 16:  The results look very nice!

page 32 bottom of page, item 3:  Here in the paper you make the
argument that the Lambda cross section is several times bigger that
the Sigma0 cross section on account of a large longitudinal coupling
as the photon gets more virtual.  It might be worth pointing out here
the consistency of the experimental finding with the Ambrozewicz
result.  However, later in the paper it is argued that the longitudinal
piece is not that large.  Is there an internal inconsistency in our
argumentation here?

page 37, near bottom, item 1: the second sentence implies that there
might be some deficiency in the data.  But that is not the message you
want to send.  Rather, the data is fine and the models have a more
difficult time because the reaction mechanism is different and
evidently more complicated for the Sigma0 than for the Lambda.

page 38 top: remove "Curiously".  It is not 'curious', but only that
Maxwell is wrong.  

page 38 energy dependence, item 1: This is a place where it would be
good to refer not only to the most recent CLAS KY photoproduction
papers but also to the earlier paper by Bradford: that was a separate
measurement with good statistics, with which the more recent results
are in agreement:

%\cite{Bradford:2005pt}
\bibitem{Bradford:2005pt} 
  R.~Bradford {\it et al.}  [CLAS Collaboration],
  %``Differential cross sections for gamma + p ---> K+ + Y for Lambda and Sigma0 hyperons,''
  Phys.\ Rev.\ C {\bf 73}, 035202 (2006)
  [nucl-ex/0509033].
  %%CITATION = NUCL-EX/0509033;%%

page 41 item 5:  again, here it would be good to also refer to the
CLAS Bradford paper mentioned above in addition to the more recent paper.

page 42 Fig 19, 20 :  Nice results, but the labels are too small to read.

page 21 Fig 21, 2223 24: What are the units on the y axis?  Nanobarns?
Also, these figures would look better is you added a horizontal line
at zero on some of the panels.

page 47 paragraph 3:  I would remove "low-level"

In general, now-a-days it is easy to make draft papers in Latex RevTex
4.1 with line numbers shown to make it easier to reference problems.
Maybe use that next time.  All you need is to invoke the lineno.sty
file.

That's all for now,
Reinhard