[Clascomment] OPT-IN: Cross sections for the exclusive photon electroproduction on the proton and Generalized Parton Distributions

[Daniel Carman]

Hyon-Suk et al.,

I have read through your draft of the cross section measurements for the DVCS/BH
processes and my comments are included below. If you have any questions, let me
know.


					        Regards,
						
						Daniel

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Page 1.
 Line 9. Use "... still remain a mystery ...".
 Line 19. Awkward structure. How about "... launched worldwide at Jefferson Lab (JLab),
   COMPASS and HERA, facilities using multi-GeV electromagnetic probes, to study ...".
 Line 50. Use "... of such a process." or "... of such processes.".

Page 2.
 Line 87. You use different significant figures for the Q2 range limits and for the xB
   range limits.
 Line 104. Need a space between quantity and units.
 Lines 124,125,126,128,130. You have introduced the prime notation for the final state
   electron and proton. Therefore you should be consistent with this notation on your
   missing mass label and your reaction labels in these lines.
 Fig. 2 caption. Line 6. Same comment as previous.

Page 3.
 Line 163. Use "On average, ...".
 Line 168. Use "200 million".
 Line 184. "... meant to compensate for various effects that are not well reproduced
   by the simulations." This factor is large enough (and worrisome enough) that I
   would like to see you include a bit more information, such as the types of effects
   that you are talking about.
 Line 186. Using elastic scattering (which is measured over a relatively narrow range
   of kinematics) to correct for reactions (DVCS/BH) measured over a relatively large
   range of kinematics, seems worrisome in regards to assigning inappropriate systematic
   uncertainties.
 Lines 198,200,203. Use "on average".

Page 4.
 Line 273. Awkward structure. How about "... simultaneously the $\phi$ distributions of
   our unpolarized and beam-polarized cross sections at a given ...".

Page 5.
 Line 323. "This considerable set of new data will provide stringent constraints on
   GPD models". But you have shown in Fig. 4 that pretty much every model well describes
   the measured data. That does not give me a sense that these data provide very much
   of a constraint. Plus the discrepancy with the Hall A data kind of muddies the waters
   on just how much of a constraint either of these datasets actually can provide.

References.
 [15]. The paper is now published.
 [18]. Is not a CLAS Collaboration paper.