[Clascomment] OPT-IN:Measurement of Exclusive pi0 Electroproduction Structure Functions and their Relationship to Transversity GPDs

[Daniel Carman]

					May 1, 2012


Dear Ivan,

I have read through your draft paper on pi0 electroproduction. I include
my comments and questions below. My general impression is that this
paper is in pretty good shape and the presentation is well motivated
and clear. Let me know if you have any questions.


			   Regards,

				  Daniel

********************************************************************
General:
 - You are not consistent in the paper with your treatment of speed
   of light units c. Sometimes you include them, sometimes you don't.
   I recommend that you simply let c=1 for all units.

Page 1:
 Abstract.
 - Line 4. Use "... were extracted as a function of $t$ ...".
 - Line 5. Use "handbag-based".
 - Line 7. Use "... $\sigma_{LT}$, while additional ...".

Page 1:
 - Line 73. Use "However, a more complete ...". 
 - Line 78. Use "subprocesses".
 - Line 89. Use "... more difficult than for $\pi^+$ for two ...".

Page 2:
 - Fig. 1. Your nu' label overlaps the outgoing proton line.
 - Line 25. Use "non-helicity-flip".
 - Line 29. Awkward sentence. I recommend "Thus $\overline{E}_T$ is a most
     interesting quantity, which we would like to access.". Note also typo
     on "interesting".
 - Line 66. Statement here is kind of awkward. You have mentioned two
     calorimeters (the EC and the IC), but here you state that the electrons
     required "appropriate energy deposition in the calorimeter". However,
     your electron ID only looks at the EC. The IC is not used for electron
     ID. This is not entirely clear from how this is written. 
 - Line 70. Use "... from pions up to a momentum of ...".
 - Line 75. Use "... efficiency, as well as ...".
 - Line 76. Use "... position cuts, to ensure ...".
 - Line 81. I suggest "... the following: The angle ...".
 - Line 93. Use "GEANT3-based".

Page 3:
 - Line 2. Use "... smaller than for the data.".
 - Line 44. The statement "There are some disagreements in the
     extracted interference structure functions ..." is kind of a
     worrying statement. A comment is essential if they disagree
     outside of the assigned systematics. Why should I believe that
     your results are correct if there is disagreement with a 
     previously published result?
 - Line 57. Use "$\overline{E}_T$" (missing T subscript).
 - Line 64. Remove comma after H-tilde.
 - Line 66. Use "... which contribute to ...". 
 - Line 67. Use "In addition, the ...".
 - Line 73. Use "... $\sigma_T$ and $\sigma_{TT}$ and, ...". 
 - Line 74. Use "... $\sigma_{LT}$, accounts moderately ...". 
 - Line 79. Use "... dominates, the cross section becomes ...". 
 - Line 82. Use "... Ref.[10], while ...".
 - Line 84. Use "... $\overline{E}_T$ is dominant, ...".
 - Line 85. Use "... well with the data.".
 - Line 87. Use "... the effect of $\overline{E}_T$." (missing period)
 - Line 88. Use "... Ref.[15] (dashed curves)" and "dominant".
 - Line 90. Use "... in their parameterization, the ...".
 - Line 92. Use "We may make a similar ...".
 - Line 93. Remove space between "$\sigma_{TT}$ and the period.
 - Line 96. Spurious period at the end of the sentence.
 - Line 111. Use "This means that the ...". 

Page 4:
 - Fig. 2. The shaded bands cannot be seen - they are far too light.
 - Fig. 2 caption:
   - Line 1. Use "vs.".
   - Line 3. Use "The shaded bands reflect ...".
 - Line 4. Use "... at the unseparated cross ...".
 - Line 6. Use ... better understand the parameterization of the
     transverse GPDs.".

References:
 - Ref.[2] - separate entries with a semi-colon.
 - Ref.[6] - Use "..., and S. Liuti, ...".
 - Ref.[16] - Use "E. Fuchey et al., ...".