[Clascomment] OPT-IN: Beam asymmetry Sigma for pi+ and pi0 photoproduction on the proton for photon energies from 1.102 to 1.862 GeV

[Daniel Carman]

						June 5, 2013


Dear Mike et al., 

I have read through your paper on the beam asymmetry in pion photoproduction and my comments 
are included below. In general this is a well written paper that is clearly presented. I 
include all of my comments below. If you have any questions, let me know.

				     Regards,

					Daniel

********************************************************************
Page 1.
 Abstract.
  - Line 2. Use "... a tagger, linearly polarized photon beam ...".
  - Line 7. Use "... both the data, as well as the SAID and Bonn-Gatchina ...".
  - Line 10. Remove the comma.
 Right column.
  - Line 56. I suggest "... in Sec. IX. They are then compared to various predictions and a ...".

Page 2.
 Left column.
  - Line 89. Use "... 50\% of its maximum nominal field ...".
  - Line 106. Use "... while for some runs, ...".
  - Line 107. Use "... of the 1.7~GeV data ...".
  - Line 108. Use "... and 1.5~GeV data sets, ...".

Page 3. 
 General comment.
  - Starting with Fig. 3, the placement of the figures is nowhere near where they are referenced
    in the text. 
 Right column.
  - Line 160. You mention a "CLAS magnetic field momentum correction" but this mention is obtuse
    at best. I think a sentence clarifying for the reader what this is all about is appropriate.

Page 4.
 General comment.
  - What are the APS guidelines for number equations? It seems that you number some and
    do not number others. I prefer all equations to be numbered.
 Right column.
  - Put a comma after the cross section equation.

Page 5.
 Left column.
  - Put a comma after the cross section equation.
  - Line before eq.(2). Use "... in eq.(1) is approximated ...".
  - Add a comma after eq.(2).
 Right column.
  - Put a period after eq.(4), not a comma.

Page 6.
 Left column.
  - After eq.(6) you should explain eq.(5) before you explain eq.(6).
  - Line right after 209. Use "... Eqs. (3) ...".
  - Line 214. In line 210 you use "mth Fourier moment" and then in line 214 you use
    "moment-n". Why switch between m and n? I suggest that you use a consistent notation.
 Right column.
  - Eqs.(14),(15),(16),(17). You should format your parenthesis better. They are too small
    for your expressions. In latex math mode, you can use constructs like $\left( ... \right )$
    and they will automatically be scaled to an appropriate size for the expression you are
    writing.
  - Line 220. Use "... typical data run owing to ...".
  - Line 229. You wrote p_para twice.
  - Line just before eq.(15). Use "which gives".

Page 7.
 Fig. 8.
  - The y-axis label sits on top of the y-axis values.
  - The 4 curves on the plot are not explained in the caption.
 Left column.
  - First line. Use "... of eqs. (14) ...".
  - Add a period after eq.(18).
 Right column.
  - Line 244. Use "... the yield of the particular meson peak ...".
  - Last line. Use "... index $i$ and \cos $\theta$ bin ...". Note that you are not consistent
    with your notation in this paper. Sometimes you write "$\cos \theta$" and sometimes you write
    "$\cos (\theta)$".

Page 8.
 Figs. 9,10,11,12.
  - The y-axis label sits on top of the y-axis values.
 Left column.
  - Line 252. Use "... of eq.(19) have ...".
 Right column.
  - Add a comma after the first equation.
  - Add a period after the last equation.

Page 9.
 Fig. 10.
  - The 4 curves on the plot are not explained in the caption.
 Left column.
  - Add a comma after the first equation.
  - Add a comma after "N_\gamma" just before the second equation.
 Right column.
  - Add a period after the first equation.
  - Remove the first comma on the line after the first equation.
  - Add a period after the second equation.

Page 10.
 Left column.
  - Line 256. Use "... by eq.(19) ...".
 Right column.
  - Add a comma after eq.(20).
  - Add a period after Sigma variance equation.
  - Add a comma after the last equation.
 

Page 11.
 Left column.
  - Put a period after the last equation.
 Right column.
  - Line 266. Use ".. but had an 18 ...".
  - Line 270. Use "... were determined ...".
  - Line 274. Use "It was assumed ...".

Page 12.
 Left column.
  - Line 278. Put a period at the end of the line.
 Right column.
  - Line 285. Use "... set was approximated ...".

Page 13.
 Left column.
  - Line 294. List this reaction consistently. You used pi+pi- on the previous page. Here you
    use pi-pi+.
 Right column.
  - Line 307. I suggest "... $M_X$ in the $\gamma p \to pX$ reaction was ...".

Page 14.
 Right column.
  - Line 324. I suggest "... to be the $\gamma p \to p \pi^0$ yield in the given analysis bin.".
  - Line 325. Use "... of the yield of the neutron peak ...".

Page 16.
 Left column.
  - Last line. Use "... mesons was determined for each ...".
 Right column.
  - Second line. Use "... bin were formed ...".

Page 18.
 Left column.
  - Starting in line 379 you have changed the style of your symbol for "phi" from what 
    you had been using earlier in the paper. Be consistent.

Page 19.
 Left column.
  - Line 483. Use "... seen in the DNPL data ...".
 Right column.
  - You have just got done with a lengthy paragraph describing in some detail the comparison
    between the pi0 data sets. Then you have a single general sentence for the pi+ data. This
    seems a little out of balance.
  - Line 528. Is the first time that you introduced the notation "CM12". I didn't know what
    this was until later on in the section. I suggest that you tell us what CM12 is when you
    first introduce this version of the SAID model.

Page 21.
 General.
  - You often put a comma between the author's name and "et al.". No comma should be here.
  - I could not find where you referred to Ref.[30] or [32] in the paper. Perhaps I missed
    them somehow, but you should double check.