[Clascomment] OPT-IN: Photon beam asymmetry Sigma for eta and eta' photoproduction from the proton

[Daniel Carman]

Dear Patrick, Barry et al:

I have read through your draft of the BSA for eta and eta' and
include my comments below. In general, the paper is quite well
written, easy to follow, and the conclusions support the data shown.
If you have any questions, let me know.

Regards,
Daniel
--------------------------------------------------------------------------------
Page 1:
 - Title: Do not include a period at the end of the title.

Page 2:
 - Left column.
   - Second paragraph. Your "standard" notation is to put parentheses
     around $\theta_{c.m.}$. However, every time you mention the
     sin**2 theta cos theta term, you leave the parentheses off. Be
     consistent with your notation throughout.
 - Right column.
   - Second paragraph. Line 3. Use "50~$\mu$m".

Page 3:
 - Left column.
   - Section 2.1. First paragraph. Line 16. Use "... photon was identified for ...".
   - Section 2.1. Second paragraph. Line 3. Drop "(provided by the drift chambers)"
      as this is redundant with the first part of the sentence.
   - Section 2.1. You did not mention anything about momentum corrections,
     uncertainties in the beam energy, or tagger energy corrections. Surely you
     must have made such corrections as they are standard. If so, they should be
     mentioned.
- Right column.
  - Eq.(5). Add a comma at the end for proper punctuation.
  - Section 2.2. First paragraph.
    - Line 7. Use "... 22.9/% [2], while the ...".
    - Line 8. Use "... eta$ with a branching ...".
    - Line 12. Use "... products were identified, ...".
    - Line 14. The final state proton in the reaction should be in math mode too.
  - Section 2.2. Second paragraph.
    - The second sentence explicitly mentions the eta' final state and ignores the
       eta final state. The Fourier-moment technique as described is applicable for
       both of your final states.
    - Line after Eq.(6). Use "... yield for a perpendicular ...".

Page 4:
- Left column.
  - Fig. 1 caption. Line 3. Use "... proton, $\pi^+$, and $\pi^-$.

Page 5:
 - Fig. 2 caption.
   - Line 1. Use "(Color online) The beam ...".
   - Line 4. Use "... dotted lines indicate SAID ... [34] are indicated by the (red)
                 long-dashed lines.".
   - Line 5. Use "... black solid lines) and without (black short-dashed lines) ...".
 - Fig. 2.
   - Add the energy units to the individual plot labels as you did for Fig. 3.
   - The reaction label at the top should use "\eta p" to be consistent with your
      notation in the paper.
   - I am not a fan of the offset y-axis and x-axis label values. I think that it makes
     the plot look clunky

Page 6:
 - Fig. 3 caption.
   - Line 1. Problem with your angle notion. Should be "$\cos (\theta_{c.m.})$".
   - Line 3. Invariant energy W should be in math mode (twice).
   - Line 8. Use "... dotted blue lines ...".
   - Line 9. Use "... solid red lines [36]), ... dashed black lines; model 4 in [37]).".
   - Line 12. Use "... dashed-dotted blue lines), ...".
 - Fig. 3.
   - The reaction label at the top should use "\eta' p" to be consistent with your
      notation in the paper.
   - As noted for Fig. 2 above, I am not a final of the offsets on the axis labels.
 - Left column.
   - Section 4. Line 1. Use "Introduction".
 - Right Column.
   - The section heading for 4.2 should match the style used for 4.1.

Page 7:
 - Left column.
   - Paragraph 2. Line 6. Use "phenomenologically "regge-ized" ...".
   - Paragraph 3. Last sentence. Use "Introduction".

References:
 - Don't include the preprint number when the paper is already published.
 - Do not use a comma before "et al.".
 - Use "CLAS Note" or "CLAS-Note".
 - Include Collaboration names that are associated with the papers after the
   author names, e.g. M. Dugger et al. (CLAS Collaboration), ..."
 - These new CLAS data need to be included in the CLAS Physics Database
    (contact Victor Mokeev for assistance) and the reference to this database
    needs to be included.