[Clascomment] OPT-IN:Observation of azimuth-dependent suppression of hadron pairs in electron scattering off nuclei

[Daniel Carman]

Dear Sebouh et al.,

I have read through the draft of your paper on the suppression of hadron pairs in electron
scattering include my comments below. Most of my comments deal with grammar/style, but I
have a few comments regarding presentation as well. Good luck with your path to publication.

If you have any questions, let me know.

Regards,
Daniel
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General:
 - Several places in the manuscript you use present tense for your verbs when you should use
   past tense. I point these out in my detailed comments below.
 - I am strongly in favor of the word choice "uncertainty" instead of "error". An error is a
   mistake. An uncertainty is an unavoidable "fuzziness" in the measurement. I point out where
   I suggest this change in your wording.
   
Page 1:
 - Line 9. Use "azimuthally opposite" - no hyphen with words ending in -ly.
 - Line 19. "... provides a way to perturb the process ...". This statement is unclear. It is
   important to be clear in your opening paragraph avoiding jargon in order to establish the
   relevance of this measurement.
 - Line 42. Use "... see Refs. [1,29] ...".
 - Line 46. Use "... to those that were created ...".

Page 2:
 - Line 80. Drop the "'s" on "CEBAF".
 - Line 85. Use "... which defined six sectors ...".
 - Line 102. Use "$p$ for momentum to be consistent with your later notation.
 - Line 103. Keep units with their values across lines. Here you would use "2~GeV".
 - Line 104. Use "... $W > 2$~GeV, and 2.2 ...".
 - Line 109. Use "Following Ref. [31], we ...".
 - Line 112. Use "... then measured all the ...".
 - Line 115. Use "... we removed kinematically ...".
 - Line 117. Use "... the pion candidates, in order ...".
 - Line 125. Use "beamline".
 - Line 128. Use "We used the electron, the leading pion, and the ...".
 - Line 139. Use "... we also measured ...".
 - Line 142. Use "By construction, $R_{2h}$ is a ...".
 - Line 154. Use "... systematic uncertainties using data and simulation studies.".
 - Line 163. Use "... of systematic uncertainty, such as ...".

Page 3:
 - Line 167. Use "The systematic uncertainties ...".
 - Line 170. Use "... at high $m_{\pi\pi}$, they reached 8.6% ..." (reduce the number of times
   "systematic uncertainties" appears in this paragraph).
 - Line 172. Use "... the systematic uncertainty dominated ...". 
 - Line 173. Use "... with a median value of 2.6\%.".
 - Line 184. Use "... 0.021, and 0.698 ...".
 - Line 186. Use "... first uncertainty is ...".
 - Line 190. Use "... experiments, respectively.".
 - Footnote line 1. Use "... statistical uncertainties were considered ...".
 - Footnote line 2. Use "... systematic uncertainties were assumed ...".
 - Line 221. Use "... suggesting that this effect does not ...".
 - Line 240. Use "... 0.020, and 0.620 ...".
 - Line 241. Use "... and Pb, respectively.".
 - Line 256. Use "behavior".
 - Line 258. Use "... reported in Refs. [15-19,21,49].".

Page 4:
 - Fig. 2. The colors of all the different data points overwhelms this figure and makes it
   difficult to parse. Furthermore, the new CLAS data do not stand out given the other non-CLAS
   data. I suggest to show the new CLAS data in color and the older non-CLAS data in black or
   gray symbols.
 - Fig. 2 caption.
   - Line 6. Use "... the systematic uncertainties, while the ...".
   - Line 8. Use "... and statistical uncertainty (added in ...".
   - Line 9. Use "... $R_{2h}$, their uncertainties and the bin edges ...".
 - Line 281. Use "... first study on the azimuthal separation and invariant mass.". 
 - Line 315. Use"... data cover a poorly ...". 

References:
 - I suggest that you include the word "Collaboration" in your references and use italic font.
   e.g. {\it (CLAS Collaboration)} and {\it (HERMES Collaboration)}.
 - Ref. 38 is a CLAS Collaboration paper.
 - Refs. [47] and [48] are out of order in your listings and should be swapped.
 - Ref. [48]. Use "... systematic uncertainties, and the bin edges.".

Page 6:
 - Line 468. Use "... of the bins, and the statistical and systematic uncertainties.".

Page 7:
 - Table I. Use "These data correspond to those shown in Fig. 2(a).
 - Table II. Use "These data correspond to those shown in Fig. 2(b).
 - Table III. Use "These data correspond to those shown in Fig. 2(c).