[Clascomment] OPT-IN: Measurement of Target and Double-spin Asymmetries for ep->epi+(n) Reaction in the Nucleon Resonance Region at Low Q2

[Daniel Carman]

Xiaochao et al.,

I have read through the draft of your pi-n asymmetry paper dated April 12. I include here
my comments. Let me know if you have any questions.


					        Regards,
						
						Daniel

************************************************************************************
General:
 - Use are not fully consistent with energy/mass/momentum units throughout. In several
   places you employed units with c=1, which was not how the bulk of the units were
   presented.
 - You have not been consistent with including "(Color online)" in your figure captions
   where color has been employed.
 - You should choose either "cross-talk" or "cross talk" and be consistent throughout.
 - In several sections the verb tense is awkward, switching back and forth from present
   tense to past tense. I have tried to catch these instances here.

Page 1:
 - Title: Use "... Asymmetries for the ...".
 - Abstract:
   - Line 6. Use "... detector that allowed ...".
 - Line 44. Use "... non-resonant amplitudes and couplings, ...".
 - Line 73. Use "... which make it possible to test ...".

Page 2:
 - Line 88. Use "... are the $P_{33} ...".
 - Line 89. Use "For the $D_{13} ...".
 - Line 91. This is awkwardly written. I might suggest "... hadron helicity conservation.
     It is expected in this regime that $A^N \to 1$, where $A^N$ is the ...".
 - Line 92. Use "... helicity asymmetry defined as:"
 - Line 99. Use "... have been calculations for the ...".
 - Line 101. A_{LL} not yet defined.
 - Line 121. Note: phi^* is not the CM azimuthal angle. In the gamma* P/piN CM, there is no
      defined CM azimuthal angle. To be clear, phi^* should be referred to as the angle between
      the leptonic plane and the hadronic plane.
 - Eq.(3). Add comma after this equation for proper punctuation.
 - Fig. 1. You need to label your "y" axis as "y-hat".
 - Eq.(5). Add comma after this equation for proper punctuation.
 - Line 131. Use "... cross section, and $\sigma_3$, $\sigma_t$, and $\sigma_{et}$ are the 
      polarized ...".
 - Line 141. Use "... i.e. the energy needed by ...".
 - Line 142. Note: epsilon in Eq.(7) is not the transverse polarization of the virtual photon.
      Better to use the standard term "virtual photon polarization parameter".
 - Lines 148-164. All of this formalism is simple textbook stuff. It should not be included.

Page 3:
 - Line 193. Use "... both the $\vec{e}\vec{p} ...".
 - Line 215. Use "... NH$_3$ target and two energies ...".

Page 4:
 - Line 247. Use "In order to reach very low ...".
 - Line 252. Use "... reaches an 8$^\circ$ ...".
 - Fig. 2. This figure is not an accurate representation of CLAS and serves only to confuse
     the reader. CLAS is rotated by 180 deg from its proper orientation with respect to
     the beamline and the large-angle calorimeter is misleadingly shown as being in all CLAS
     sectors. Also, the dashed region about the R2 DC is not explained.
 - Fig. 2 caption. Line 2. Use "A new Cherenkov detector consisting of 11 segments ...".
 - Fig. 3. The lines on the figure showing the light paths are too dim to be appreciated.
 - Line 276. Use "systematic uncertainties.".
 - Line 278. Use "... removed (out), respectively.".
 - Line 279. Use "... measured by both a Moller and a Mott ...".
 - Line 282. Use "... for EG4 were the frozen ...".
 - Line 283. Use "... ND$_3$ targets dynamically polarized at 1~K with a 5-T field. These were
      the same targets used for ...".
 - Line 294. Use "... hereafter referred to as the long and short ...".
 - Line 295. Your opening quotation marks on "banjo" are not of the proper sort.
 - Line 298. Use "... can be found in Ref.[35].".
 - Line 302. Use "... banjo could be determined ...".
 - Line 303. Use "... beam could not be directly ...".

Page 5:
 - Fig. 4 caption.
   - Line 2. Use "The 1.0-cm long ...".
   - Line 4. Use "... period. They were called the ...".
   - Line 7. Use "... positions; they were called the ...".
 - Line 308. Use "... thickness was placed in ...".
 - Line 310. Use "Empty target cold either be ...".
 - Line 311. Use "... the $^4$He could be completely ...".
 - Line 325. Use "... uncertainties that limited ...".
 - Line 343. Use "... is was decided that the asymmetries ...".
 - Line 344. Use "... scattering would be used to ...".
 - Line 346. Use "The methods and results ...".
 - Line 347. Use "Section III D".
 - Line 352. Use "Section III G".
 - Line 358. Use "For each event, we required that two particles be detected with the correct ...".
 - Line 361. Use "Each particle was also required to have valid information from all detectors
       (DC, EC, TOF, and CC) and have reconstructed momentum greater than 0.3~GeV/$c$ ...". Note
       if you wish to use "SC" for the TOF system, then you need to be consistent with your usage
       in the paper. At present you switch back and forth.
 - Line 366. Use "... energy deposited in the EC: ...".
 - Line 367. Use "... in GeV/$c$, and the energy deposited in the inner ...".
 - Line 368. Use "... of the EC such that $E_{in ...".

Page 6:
 - Line 369. Use "We also required there to be only one hit in the CC, with this signal consistent
     with those from the EC and TOF in ...".
 - Fig. 5 caption.
   - Line 5. Use "... and protons, and protons and heavier particles.".
 - Line 382. You use "z" here but have not defined the CLAS coordinate system as of yet.
 - Line 390. Use "... the detectors, but could also ...".
 - Line 392. Use "... GDH sum, which only ...".
 - Line 394. You statement "not all six DC sectors were turned on during the run." is a worrisome
     statement. What DC were turned on? How can you measure phi^* distributions when you don't have
     full azimuthal coverage in the lab? A bigger question might be why one would take CLAS data without
     the tracking detectors turned on?
 - Line 417. Use "The exact energies were ...". By the way, you quote beam energies to three significant
     figures. What is the uncertainty on these energies?
 - Line 431. The last two sentences of this paragraph "It was found that for beam ..." only serve to add
     confusion without any beneficial content. I suggest that you remove them.

Page 7:
 - Fig. 6 caption. Were your gray bands drawn arbitrarily? How do you know the beam polarization for the
    run extents between Moller measurements?
 - Line 453. Use "... effect that affected ...".
 - Line 461. Use "... described in Ref.[44] and the results ...".
 - Line 462. Use "... are given in Ref.[43]. For sector 6 equipped ...".
 - Line 467. Use "... e' \pi^+ \pi^- X$, and ...".
 - Fig. 7 caption.
   - Line 5. Use "... 14~$\mu$m ...".
 - Fig. 7. It is now clear from this figure why your events are in the z-range from -106 to -96 cm given
    the words that you have used to describe your target.
 - Fig. 8 caption.
   - Line 1. Use "... for the $e + p ...".
 - Fig. 8. Should not you compare the peak centroid and width before and after corrections?
 - Line 484. Use "Section II C".

Page 8:
 - Line 486. Use "... an alternate method had to be used.".
 - Line 505. You should note that $Q = \sqrt{Q^2}$.
 - Line 522. Use "... $P_bP_t$ value extracted ...".
 - Line 539. Use "... charge of the carbon ...".
 - Eq.(31). Add a comma (not a period) after the equation for proper punctuation.
 - Line 546. Use "... bound-nucleon fractions of the ...".
 - Table II caption.
   - Line 1. Use "Material used for the EG4 ...".

Page 9:
 - Eq.(32). Put a comma after the equation for proper punctuation.
 - Line 557. Use "from the NH$_3$ target.".
 - Line 558. Use "... correction to the elastic ...".
 - Line 560. Use "... /$c$)$^2$ could not be used because of ...".
 - Line 569. Use "After the $P_bP_t$ value was extracted ...".
 - Line 571. Use "... there was no systematic ...".
 - Line 583. Use "... comparing the $P_bP_t$ value extracted ...".
 - Line 601. Use "... using the $x_ ...".
 - Fig. 9 caption.
   - Line 14. This sentence is extremely awkward as written. I suggest "Note that the ... for the chosen
       packing factor we have scaled up the carbon data and then subtracted the extra helium to ...".

Page 10:
 - Line 639. Use "... analysis that has only ...".
 - Line 640. Use "Section III D".
 - Line 657. Use "... from Eq.(42) ...".
 - Fig. 10 caption.
   - Line 12. Use "dilution uncertainties" and "statistical uncertainties".
   - Line 15. Use "... carbon data and then subtracting the extra helium ...".
   - Line 16. Use "The results for the dilution ...".
   - Line 17. Use "... is shown on the bottom plot, ..." Also your text overlaps your vertical lines. It
      should be moved further away.

Page 11:
 - Line 670. Use "... due to the packing ...".
 - Line 674. Use "... used in the $P_bP_t$ ...".
 - Line 676. Use "... uncertainty in the semi-inclusive ...".
 - Line 679. Use "... factor was varied ...".
 - Line 681. Use "... were used for the evaluation ...".
 - Line 682. Use "... $A_{UL}$, the uncertainty ...".
 - Line 694. Use "... factor was cross-checked ...".
 - Line 696. Use "... factor was determined ...".
 - Line 698. Use "The kinematic dependence of the ...".
 - Line 700. Use "... have been studied, and multi-dimensional fits ...".
 - Line 713. Use "The resulting two fits were then ...".
 - Line 728. Use "In this section we estimate this ...".
 - Line 730. Use "... correction was made to the extracted ...".
 - Line 740. Use "... $B=5$~T and ...".
 - Line 741. I do not know what is meant by "T_S = 1 ~ 1.5 K".
 - Line 744. Use "... higher-order terms $[{\cal{O}}(x^5)]$ ...".
 - Line 745. Use "... Applying the magnetic moment ...".

Page 12:
 - Table III caption.
   - Line 2. Use "... three uncertainties ...".
   - Line 5. Use "Section II C" and "... were used to correct ...".
   - Line 7. Use "... uncertainties were used as systematic ...".
 - Eq.(47). Add a comma after the equation for proper punctuation.
 - Line 753. Use "... additional factor of ...".
 - Line 771. Use "... correction was then applied ...".
 - Line 773. Use "... $N{...}$, where each event ... as 1, we first divided 1 by ...".
 - Line 774. Use "... the sum was taken ...".
 - Line 775. Use "... Section III E ...".
 - Line 776. Use "... this way were integrated ...".
 - Line 778. Use "... bins could not be corrected ...".
 - Line 797. Use "... factor, as well as the thickness ...".
 - Line 801. Use "... For the asymmetry ...".

Page 13:
 - Table IV caption.
   - Line 1. Use "... due to the target ...".
 - Line 810. Typo on "logarithmically".
 - Line 821. Use "Section III H".
 - Line 822. Use "... bin was corrected for ...".
 - Line 824. Use "... were summed over ...".
 - Line 825. Use "... sums were used ...".
 - Line 833. Use "... where there was no data ...".
 - Line 834. Use "... was taken as the calculated ...".
 - Line 842. Use "Section I A".
 - Line 846. Use "... ranges, the $A_{UL}$ results ...".
 - Line 847. Use "... as a function of $W$ for ...".
 - Line 849. Use "... as a function of $\phi^*$ ... clear that the models ...".
 - Figs. 12 and 13. Why were these kinematic ranges chosen? They are presented as random choices and then
     some very specific observations are made. I think some further context is needed here to make this
     presentation a bit crisper.
 - Line 853. Use "... $A_{LL}$ versus the invariant ...".
 - Line 855. Use "... there appears to be ...".
 - Line 856. Use "... change in $A_{LL}$ in the region of the $D_{13}(1520)$ and the $F_{15}...".
 - Line 860. Use "Section I".
 - Summary section: This section does not seem all that well thought out. A sign change is mentioned in
   one observable, but why should anyone care? You need to explain the relevance and why this is so
   important. The second observable is barely mentioned. Again, why is this data important. The generic
   statement that "it can be used to improve models" is not particularly satisfying after reading a
   dozen pages of analysis details. There are some differences in the calculations when compared to the
   data, but what specific constraints can these data improve upon for the N* states mentioned?
 - Line 865. Use "... data on the target and double-spin asymmetries ...".

Page 14:
 - Fig. 12. Your caption for the Q2 values of the top row and what is printed on the plots do not match.

Page 16:
 - Fig. 13 caption.
   - Line 1. Use "... $A_{LL}$ for the ...".
 - 

Page 17.
 References:
 - Put the references in the order cited in the paper.
 - Ref.[19] is not complete as written. For the other "Ph.D." theses listed, you gave the full title.
 - Ref.[20] is not a proper reference as it points to site that is not public.
 - Ref.[32] is not a CLAS Collaboration paper.
 - You need to enter these data into the CLAS physics database and give that reference in the paper.