[Clascomment] OPT-IN: Measurement of the beam asymmetry Sigma and the target asymmetry T in the photoproduction of omega mesons off the proton using CLAS at Jefferson Laboratory

[Daniel Carman]

Dear Priyashree, Volker et al:

I have read through your draft paper on the omega meson photoproduction
spin observables from the FROST experiment and include my comments below. 
In general, this paper was well constructed, the presentation is well
thought out, and the data are very nice. If you have any questions on my
comments below, let me know.

Regards,
Daniel

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Page 1:
 - Right column.
  - Line 72. Use "... photon, as well as ...".

Page 2:
 - Left column.
  - Line 86. "These observables impose tighter constraints on theoretical models."
     Tighter than what? Your thought does not seem complete.
  - Line 93. Use "... 13-16], and the ...".
  - Line 132. Use "... selection are discussed ...".
  - Line 133. Use "... technique for extracting ...".
 - Right column.
  - Fig. 1. I am curious as to what other folks think, but I find this figure absolutely
    impenetrable. It is far too busy and I just cannot make sense of it. Perhaps if this
    was separated into two figure, one for each of your coordinate systems.
  - Line 145. Use "... beam polarization, as ...".

Page 3:
 - Left column.
  - Line 169. Use "... be employing a coherent ...".
  - Line 203. Use "... Since the electron beam helicity state ...".
 - Right column.
  - Line 221. Use "... 116.1^\circ \pm ...".
  - Line 223. Use "... -63.9^\circ \pm ...".
  - Line 226. Use "... into the CLAS acceptance region ...".
  - Line 228. Use "... two unpolarized targets were placed ...".
  - Line 231. Use "... systematic studies. They were placed ...". (Remove the "Both targets ..."
      sentence.
  - Line 232. Use "... downstream than the butanol ...".
  - Line 233. Use "... approximately $\Delta z = 9$~cm ...".

Page 4:
 - Left column.
  - Fig. 3 caption. Remove the italics font.
  - Fig. 3. Why is this plot truncated at 1.5 GeV? Perhaps you should make clear the momentum
     range of your final state particles.
 - Right column.
  - Line 283. Use "... identified in the $\beta ...". Also remove the italics font.
  - Line 294. Use "... $\pi^+$ and $p$ four-vectors ...".
  - Line 301. Use "An example of our confidence- ...".
  - Line 310. Replace "p" with "CL" as "p" is already used for the proton.

Page 5:
 - Left column.
  - Line 9 in unnumbered paragraph. Use "... asymmetry is detailed in Refs.~[10,18]."
  - Fig. 5. Why is the peak shifted from the expected mass by ~4 MeV? This is after
     kinematic fitting. Something seems odd here.
 - Right column.
  - Line 322. "... is the $\pi$ mass". Give the charge state as +/- mass is not the same as 0
     mass.
  - Line 342. Use "Voigtian".
  - Line 350. and 353. Use "least-squares".

Page 6:
 - Left column.
  - Line 382. Strike the word "true". It is not necessary.
 - Right column.
  - Line 411. Use "... 2.025~rad ...".
  - Line 414. Use "... as discussed in Section ...".

Page 7:
 - Left column.
  - Fig. 7 caption. Last line. What is meant by "(same frame)".
  - Line 427. Use "... holding field. More details on these corrections are available ...".
  - Line 428. Start a new paragraph with the sentence "For the extraction ...".
 - Right column.
  - Line 464. Use "... from the FROST data, ...".
  - Line 465. Use "... had to be removed (as detailed below)."

Page 8:
 - Right column.
  - Eqs (17) and (18) have the same angle for the sine function. How is this consistent
    with your description of the two different offset angles on line 411?

Page 9:
 - Fig. 8, 9, 10 captions. Use "... background subtraction. The horizontal ...".
 - Note: All of your data should be entered into the CLAS physics database before submission.
   A reference should be added to your bibliography referencing this db.

Page 10:
 - Left column.
  - Line 559. Use "... [14] (2006 data - magenta ... [16] (2015 data - blue ...".
 - Right column.
  - Line 595. Use "statistical uncertainties".
  - Line 597. Use "... All of this ...".

Page 11:
 - Section C. 
   - I do not like the presentation of Table I. I cannot justify the values listed in
     Table I given what is presented in the text. You should clearly separate the point
     to point systematics from the scale-type systematics. The values in Table I should
     clearly reflect the values given in the text. Also, it is not clear if your gray
     systematic bands include only one source of your point-to-point systematics or all
     of them.

Page 12:
 - Left column.
  - Line 692. Use "... data, which utilized ...".

Page 13:
 - Left column.
  - Line 741. Use "In the FROST $\gamma p \to p \omega$ data presented here, large beam ...".
 - Right column.
  - Line 789. Use "... target asymmetry $T$ ...".
  - I find your "Summary" section a very weak way to end this paper. You have only given a
    few cursory words describing the observables but this section (which should be entitled
    "Summary and Conclusions") has absolutely no physics "meat". You should at least say what
    these data may be used for given their kinematic range and their precision and you should
    certainly connect back to all of the ideas raised in the Introduction section.

References:
 - Put the references in the order cited in the text.
 - I found several of your references were not cited, namely [30], [31], and [32].
 - Ref. [21] is not a "CLAS Collaboration" paper.
 - Ref. [28] should be given with a URL. This is a publicly accessible document.