OPT-IN:Polarization Observables T and F in the γp→π0p Reaction at CLAS

[Daniel Carman]

Hao, Igor, Steffen,

I have read through the draft of your FROST pi0p paper. It was a very enjoyable read
and a very nice set of results. I included my comments below. Let me know if you have 
any questions.

					        Regards,						
						Daniel

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Page 1:
 - Line 44. Use "... quark model are incorrect.".
 - Line 53. Use "... summarized in Refs. [2,3].".
 - Line 62. Use "... target is needed ...".
 - Line 64. Use "... amplitudes that does not exist ...".
 - Line 68. This paper would be enhanced by defining the different observables here for
   for the reader E, Sigma, T, and F.
 - Line 69. Use "... such as Refs. [6,7] ...".

Page 2:
 - Line 76. Typo on "transversely".
 - Line 78. Use "... section, $P_\odot$ is the degree of circular polarization of the photon
   beam, ...".
 - Fig. 1 caption.
   - Line 2. Use "circularly polarized".
   - Line 3. Typo on "transversely".
 - Line 99. Use "CEBAF Large Acceptance Spectrometer". Also include the reference to the
   CLAS NIM paper (Mecking et al.) here.
 - Line 106. Use "(LINACs)".
 - Line 112. Use "bremsstrahlung".
 - Line 113. Use "longitudinally polarized". (no hyphen with "-ly" words)
 - Line 116. Use "... the electron beam energy ...".
 - Line 131. Use "... polar angle range up to ...".
 - Line 140. Use "polarization direction". (no hyphen)
 - Line 146. Use "beamline". (one word)
 - Line 151. Need references for "TEMPO" and "PCTFE". (I assume these are some type of material.)
 - Line 157. Use "... background and were used to study the instrumental asymmetries.".

Page 3:
 - Line 162. Use "... orientation, which enters ...".
 - Line 168. Use "... was used, which was ...".
 - Fig. 2 caption. Line 1. Use "... in the lab and reaction frames.".
 - Line 173. Use "... determined in Ref. [16].".
 - Line 177. Use "... polarization was constant ...".
 - Line 179. Use "... reported in Ref. [8].".
 - Line 193. Use "... major components, including the torus ...".
 - Line 196. Use "... CLAS detector is shown in Fig. 3.".
 - Fig. 3 caption.
   - Line 2. Use "calorimeters, and time-of-flight counters.".
   - Line 4. Use "... the entire $4\pi$ solid angle except ...".
   - Line 5. Use "This figure is from Ref. [18].". This figure has been used many times in many papers.
     It did not originate in Ref. [18]. I am not sure a reference is required here.
 - Line 199. Use "... Table I, which lists ...".
 - Line 205. Use "... listed was 3.082~GeV.".
 - Line 210. Use "beamline".
 - Line 211. Use "... vertex is shown in ...".

Page 4:
 - Table I caption. Line 1. Use "circularly polarized".
 - Table I column headings. Capitalize "Range" and "Pol.".
 - Line 222. Use "... of the observables $F$ ...".
 - Line 225. Use "... vertex approaches the end ...".
 - Line 231. Use "... of 2~cm was applied ...".
 - Line 236. Use "bremsstrahlung".
 - Line 248. Use "... in each event, $\Delta t_p$, was taken ...".
 - Line 249. Use "... which was calculated ...".
 - Line 257. Use "... other positively charged particles.". (The rest of this sentence is unnecessary as you
   state this point on line 260.)

Page 5:
 - Fig. 5 caption. I recommend "... the black curves indicate the cut limits used to select the protons
   used in the analysis.".
 - Line 288. Use "... 2.3~GeV/$c$, a cut ...".
 - Fig. 6 caption. Remove "(red)" at the end as you already stated "The red curve ...".
 - Line 295. Use "miss-mass-squared".
 - Line 310. Use "... reconstructed momentum of the protons". (spurious "the momentum" here)

Page 6:
 - Line 323. Use "The data were sorted in 34 bins ...".
 - Line 324. Keep units with their values instead of allowing them to split across lines using "0.03~GeV".
 - Line 325. Use "... and in 20 bins of $\cos \theta_\pi^{cm}$ from ...".
 - Line 328. Use "... from both the butanol ...".
 - Line 329. Use "... examples of the missing-mass ...".
 - Line 333. Use "... target and the gray ...".
 - Line 383. Use "... the fit ranges also increase.".
 - Line 385. Use "... red curves and the scaled ...".
 - Comment: You are not consistent in your angular notation. You switch between "$\cos \theta$", $\cos (\theta)$,
   "$\cos \theta_\pi^{cm}$", and "$\cos (\theta_\pi^{cm})$". I prefer consistency of the notation in the text and
   in the figures. I think that "$\cos \theta_\pi^{cm}$" is the most appropriate notation throughout.

Page 7:
 - Table III caption. Line 2. Use "... from the butanol ...".

Page 9:
 - Eq.(25). It is not clear to me how this acceptance function is used and how the parameters are determined.
   There is not enough detail in the text for explanation.
 - Line 511. "after determining the acceptance effect". What does this mean? I do not understand what you are
   trying to say here. Also it is not clear in Eq.(30) if you acceptance correct your yields or not.
 - Line 519. Use "... are the variances of $h$, $u$, ...".

Page 10:
 - Line 565. Use "... which enters through ...".
 - Line 567. Use "... give $\tan \varphi_0$ and ...".
 - Line 585. Use "However, the simplified expression,". (drop "for $\tan \varphi_0$")
 - Line 613. Use "beam-charge asymmetry".
 - Line 638. Use "$W$".
 - Line 643. Use "... would lead to uncertainties ...".

Page 11:
 - Table IV caption. Add a period at the end for proper punctuation.
 - Table IV item list. Use "Beam-charge asymmetry".
 - Line 648. Use "... up to 4\%, which ...".

Page 12:
 - Line 721. Use "... nucleons is accounted for ...".
 - Line 745. Use "... analysis for data from ...".
 - Line 759. Use "In the case of the observable ...".
 - Line 762. Use "In the case of the observable ...".
 - Line 770. Use "... the extraction of the observable ...".
 - Line 780. Use "Results of the observable ...".
 - Line 792. Use "... points in bins that are ...".
 - Line 812. Use "... for the observable ...".
 - Line 814. Use "... for the observable ...".
 - Line 817. Use "... groups have included ...".
 - Line 818. Use "... in the databases.".
 - Line 819. Use "... of the polarization observables ...".

Page 13:
 - Figs. 9, 10, 11. Your systematic uncertainty bands appear to be zero width!
   Something seems wrong here. Your systematic uncertainty should be 5%, which
   amounts to half of your tick spacing on the y-axis. Please check.
 - Fig. 9 caption.
   - Line 1. Use "... of the observables ...".
   - Line 5. Use "... red and purple, respectively.".
   - Line 7. Use "... yellow and teal, respectively.".
   - Line 8. Use "... shown as circles and data from CBELSA/TAPS ... are shown as squares".
 - Line 833. Use "... such as Ref. [6] ...".
 - Line 834. Use "2285~MeV". (Keep units with their values.)
 - Line 844. Use $T$ and $F$.
 - Line 850. Use "... that preserves unitary ...".
 - Line 858. Use "... have a noticeable ...".
 - Line 875. Use "J\"uBo".
 - Line 876. Use "... as the present ones, are ...".
 - Line 879. Use "... two states, we find ... in the photocouplings ...".
 - Line 881. Use "... and $N(220)9/2^+$.".

Page 14:
 - Figs. 10, 11. The font size is too small to be readable for your axis titles, axis labels,
   and W values. You could make things bigger by turning off the labels and axis values for the
   inner plots and eliminating the space between the plots. Only include titles and axis labels
   along the left-most size of the full figure and along the bottom-most edge of the full figure.
 - Fig. 10 caption. Line 3. Use "... blue, and green, respectively.".
 - Line 898. Use "The polarization observables ...".

Page 15:
 - Fig. 11 caption. Line 3. Use "... blue, and green, respectively.".
 - Line 900. Use "... in previous measurements, ...".
 - Line 903. Use "... reaction and to study this reaction channel in a much larger ...".
 - Acknowledgments. Add the usual CLAS acknowledgments and JLab contract number.

Page 16:
 - References:
   - Ref. [12] is not appropriate at line 107 for the 6 GeV era of the program. It is a 12 GeV program
     paper. 
   - Ref. [17]. The CLAS NIM paper (Mecking et al.) is not a CLAS Collaboration paper. So remove the
     Collaboration affiliation.
   - Ref. [18]. Use "(CLAS Collaboration)".
   - Ref. [20]. Provide URL link to the note.
   - Ref. [21]. Provide URL link to the note.
   - Ref. [23]. This is incomplete. Give a reference to a CERN write-up or a publication.
   - Ref. [25]. Use "... isobar model - MAID2007, ...".