[Clascomment] OPT-IN: Near Threshold Neutral Pion Electroproduction at High Momentum Transfers and Generalized Form Factors

[Daniel Carman]

					October 28, 2012


Dear Puneet,

I have read through your threshold pion electroproduction paper draft dated
Oct. 24, 2012. My comments are included below. Let me know if you have any
questions.

			   Regards,

				  Daniel

********************************************************************
General:
 - As the paper will be published in black and white, you need to make sure that the
   paper is fully readable in black and white. Throughout the paper you refer to curves
   and points of a given color both in the text and in the figure captions. This will
   need to be remedied.
 - You are not consistent with your epsilon notation throughout. Sometimes you use
   "\epsilon" and sometimes "\varepsilon". 
 - You initially use "electroproduction" and then change to "electro-production". Use
   consistent language throughout.
 - You introduce the "TOF" system in CLAS as "SC", but then refer to it as the TOF system
   for the remainder of the paper. This should be cleaned up.
 - Folks typically refer to a CM azimuthal angle. But the azimuthal angle does not have
   a proper meaning in single meson electroproduction. The incident photon, target proton,
   scattered baryon, and scattered meson all lie in a plane.

Page 1.
 - Line 16. Use "... photo-production and are known as the low ...".
 - Line 29. Use "... \to 0$), these predictions were ...".

Page 2.
 - Line 83. Remove the comma after "constant".
 - Line 115. Use "... factors for pion electroproduction ...".
 - Line 133. Use "... compared with the theoretical ...".

Page 3.
 - Line 157. Remove the comma after "frame".
 - Line 178. Add a comma before "respectively".
 - Line 182. Remove the comma after "multipoles".
 - Line 187. Remove the comma after "reaction".
 - Line 188. Use "CEBAF Large Acceptance Spectrometer".
 - Line 203. Use "... solid angle coverage with typical ...".

Page 4.
 - Fig. 2 caption.
   - Line 1. Use "A three-dimensional view ...".
   - Line 4. Use "electromagmetic calorimeters".
 - Line 239. Use "... through the EC, they shower ...".
 - Line 241. Remove the comma after "energy".

Page 5.
 - Fig. 4 caption.
   - Line 1. Use "... of $p$. The curves show the $\pm$3.5 ...".
 - Line 280, 283. Use "$z$-vertex".
 - Line 301. Use "... holes in the drift chambers ...".
 - Line 316. Use "... edges of the $\phi_p$ ...".
 - Line 318. Use "... lower bounds on $\phi_p$ are ...".

Page 6.
 - Fig. 5 caption.
   - Line 1. Use "Sector".
   - Line 2. Use "... slices. The blue curves show the $\phi_e$ ...".
   - Line 3. Use "... selection and the red curves show the ...".
 - Fig. 6 caption.
   - Line 1. Use "vs.". Use "Sector".
 - Line 323. Typo on "constraint".
 - Line 342. Use "... electrons lose energy.".
 - The paragraph beginning at line 345 and that beginning at line 355 are not crisply
   written making it very hard for me to follow. The ellipse that you use as a primary
   cut needs to be motivated. It comes out of nowhere and seems completely arbitrary.
   Also you introduced two different angle defintions in Eq.(19) and (20), but you only
   talk about the first one. What is the purpose of introducing the second definition and
   then plotting it or using it. Also, I do not know what you are referring to when you
   use the term "fringe" on pp. 6 and then again in the Fig. 8 caption (where you talk about
   two fringes).

Page 7.
 - Fig. 8 caption.
   - Line 10. Use "... subtraction cuts, the blue curve ... cuts, and the red curve ...".
 - Line 371. Use "... cut on $M_X^2$ from ...".
 - Fig. 9. The reduced chi**2 values of 3.5 and 3.1 show that your fit functions do
   not accurately reflect the parent distributions. This is likely because of your
   elliptical cut. Fig. 8 shows that this cut asymmetrical cuts into the BH contributions
   and thus using a Gaussian to model the remnant in Fig. 9 is not appropriate.
 - Fig. 9 caption.
   - Line 8. Use "... is the goodness of fit ...".
 - Line 388. Use "... and the non-resonant backgrounds ...".
 - Line 398. Use "... extrapolations of the fits to the existing ...".
 - Line 400. The language "a little bit beyond" is too loose. Be quantitative.

Page 8.
 - Line 420. Use "... called the GSIM Post Processor ...".
 - The paragraph beginning at line 423 is written kind of loosely. The usual statement
   that folks make is that the same codes are used to process both data and MC to be sure
   that they are treated the same way. You use the language "processed similarly", which
   is quite vague.
 - Line 424. Use "... from the experiment ...".
 - line 425. Typo on "level".
 - Line 426. Use "... similarly to the experimental ...".
 - Line 428. Use "... for the cross section calculations.".
 - Eq.(22). Add a comma after the equation.
 - Fig. 10 caption.
   - Line 2. Use "... shows the corrections for a different ...".
 - Eq.(23). Add a comma after the equation.
 - Line 454. Use "... events from the experiment ...".
 - Line 463. Add a comma before "where".

Page 9.
 - Fig. 11 caption.
   - Line 3. Use "... using the MAID2007 ...".
 - Line 493. The empty target cell was not filled with air, but hydrogen gas.
 - Line 498. Add a comma at the of the line and use a period after Eq.(25).
 - Line 513. Is the 11% deviation independent of kinematics Q2, W, cos theta, phi? Was
      this studied and verified?
 - Are your cross sections bin-centered or bin-averaged? An explicit statement should
   be made.

Page 10.
 - Line 541. Use "... in this analysis, the parameters ...".
 - Why are there not systematic uncertainties associated with your determined radiative
   corrections and with your event generator. My guess is that these are likely just as
   big as your biggest source in Table II. What has been done to study both sources?
 - Table II caption.
    - Line 1. Use "... for the differential cross ...".
 - Line 626. Use "... as a function of $\cos ...".
 - Line 630. Use "... systematic uncertainties is show as the gray bands.".

Page 11.
 - Fig. 13 caption.
   - Line 2. Use "statistical uncertainties".
   - Line 2. Use "The size of the estimated ...".
   - Line 3. Use "The prediction from LCSR ...".
 - Line 634. Use "... 14) is generally in good agreement with the ...".
 - Line 659. Use "... the MAID2007 ...".
 - Line 667. Use "... [14], one must extract ...".

Page 12.
 - Figs. 14, 15, 16. - The gray bands are very hard to see.
 - Line 678. Use "... of the helicity amplitudes ...".

Page 13.
 - Line 680. You have not used "c.m.s." before. Use "CM system".

Page 14.
 - Line 692. Use "... in a similar range of ...".
 - Line 696. By "smaller", do you mean better or worse compared to the present work?
 - Line 700. Remove comma after "[32]".
 - Line 701. Add a comma after "GeV".
 - Line 737. Use "... using the UIM ...".
 - Line 738. Use "... results for the ...".
 - Line 749. Note that Q2 on the right side of the equation must be in GeV2.
 - Line 751. Use "... as a function of $Q^2$".
 - Line 752. Use "... include statistical and systematic ...".
 - Line 755. Use "systematic uncertainties".
 - Line 763. The bit beginning "The "pure" LCSR ..." does not form a proper sentence.
     I would hazard a rewrite, but I am not sure what you are trying to say.

Page 15.
 - Line 779. Use "The overall trends ... are similar ...".
 - Line 783. Use "... results for the ...".
 - Line 802. Use "... of all kinds, ...".
 - Line 806. Remove both instances of "the" on this line.
 - Line 809. Use "... zero, differs ...".
 - Line 836. Use "30\%".
 - Line 838. Use "... for comparison.".