[Clascomment] OPT-IN: Measurement of the Sigma Pi Photoproduction Line Shapes Near the Lambda(1405)

[Daniel Carman]

					December 21, 2012


Dear Kei and Reinhard,

I have read through your paper on the L(1405) and include my comments below.
It has been very interesting to follow this analysis through the various working
group presentations to see it culminate into this very nice result. It clearly
demonstrates a lot of hard work on an analysis that was quite tricky. If you
have any questions, let me know.

My comments are referenced to the paper version dated Dec. 14, 2012 that was
provided for the CLAS review.


			   Regards,

				  Daniel

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Page 2.
 - Line 17. I do not know what you mean with the statement "and lead to a deeper understanding
     of structures that populate this mass region." Are you speaking of disentangling the
     contributing resonant contributions and non-resonant backgrounds? I think your statement 
     could be made a bit more crisply.
 - Line 23. Use "... theory [4-6] combines chiral ...".
 - Line 37. Use "... model [12], the $\Lambda(1405)$ ...".

Page 3.
 - Line 44. Use "$S$-wave".

Page 4.
 - Line 100. Use "... $K^+$, $p$, and ...".

Page 5.
 - Fig. 2. Third column. Use "$\pi^0 \gamma$ (64\%)". (Missing space before B.R.)

Page 7.
 - Line 130. Use "... measured momenta, while ...".

Page 8.
 - Line 158. Use "... the $\Lambda(1405)$, is below ...".
 - Line 161. Use "... $K^+\pi$, where $Y$ ...".

Figs. 5, 6, 7, 8, 9, 10, 11, 12, 16, 17.
 - You W labels on the plots do not have units listed. I would recommend that these
   figures be remade with GeV units explicitly included.

Page 10.
 - Line 176. Use "... final state, the combination ...".
 - Line 179. Use "... $\Lambda \to p \pi^-$.".
 - Line 182. Use "... required that MM$^2$ be ...".

Page 11.
 - Line 194. Use "... for this run were not ...".

Page 14.
 - Line 209. Use "... primary trigger and for the measured $\sim$85\% data acquisition livetime ...".
 - Line 212. Use "... of interest and also the ...".
 - Line 213. Use "... background reactions in each channel ...".
 - Line 216. Use "... fraction ratios, scaled this down ...".
 - Line 222. Use "... \to K^+ \Sigma^0(1385)$ ...".

Page 15. 
 - Line 237. Use "$P$-wave".

Page 16. 
 - Line 259. Use "... relative height of each ...".

Page 17.
 - Fig. 15. Why do you not quote the reduced chi**2? This allows you to make a definitive
     quantitative comparison.
 - Line 295. Use "... $Y^*(1670)$, which shows ...".

Page 18.
 - Line 308. Use "... limited statistics, we sum ...".
 - Line 318. Use "... even after several iterations.".
 - Line 320. The sentence "An appropriate portion of any fit discrepancy compared to the data ..."
     makes no sense to me. What are you trying to say here?

Page 19.
 - Fig. 16. The magenta points, especially in relationship to the red points, are not easily seen
     on the figure.
 - Fig. 16 caption. Line 4. Use "... histogram at the bottom shows the ...".
 - Line 333. Use "... distributions at the ...".
 - Line 340. Use "... energy $W$, we show ...".
 - Line 342. The statement "... we neglect these differences for now." is not clear. What differences
     are you neglecting? Are you referring to the different cos theta ranges?

Page 21.
 - Line 349. Use "... 2.8~GeV, the mass ...".
 - Line 357. Use "... 1.7~GeV, but we compare ...".

Page 22.
 - Line 372. Use "Overall Systematics of the Run".
 - Line 376. Use "... of the intermediate ground state hyperon.".
 - Line 377. The systematic assigned for the Delta TOF cut doesn't make sense to me. If you vary the
     cut on the data, you see a 2-6% change in the yield. That is not a systematic uncertainty source.
     That is expected because you are changing the integration range. The systematic that you should
     study instead is the variation in your acceptance-corrected yield when you vary your Delta TOF
     cut on both data and MC.
 - Line 395. Use "... energy and angle, the $\Sigma \pi$ ...events was fit with a ...".

Page 23.
 - Line 414. Use "If there was any ...".
 - Line 417. Use "Fig. 19(b)".

Page 25.
 - Line 444. Use "... can then be obtained ...".
 - Eq.(16). Add a comma at the end of this equation.

Page 26.
 - First line of page. Use "that is, the interference ...".
 - Eq.(19). Add a comma at the end of this equation.
 - Eq.(20). Add a comma at the end of this equation.
 - Three lines before Eq.(21). Use "... be a "1", let it be the ...".
 - Line 467. Use "$S$-wave".

Page 29.
 - Line 520. Use "... below the centroid.".
 - Line 538. Use "... and one $I=1$ ...".

Page 31.
 - Line 557. Use "... of the broad $I=1$ ...".

Page 33.
 - Line 594. Use "$P$-wave".
 - Line 597. Use "$P$-wave" and "$S$-wave" in this line.
 - Line 599. Use "$\Sigma \pi$" to be consistent with usage elsewhere.
 - Line 604. Use "... in part by Breit-Wigner $I=1$ amplitudes ...".

Page 34.
 - Line 621. Use "... that the choice of one $I=0$ and ...".
 - Line 622. Use "... paper led to the best fit among ...".
 - Line 623. The sentence "Similar results were obtained using two $I=0$ and one $I=1$ amplitude ..."
     came as quite a surprise to me, especially presented at the very end. If the fit results using
     one I=0 and two I=1 amplitudes are essentially the same equivalent (as you seem to be suggesting
     here) to the fit results using two I=0 and one I=1 amplitude, why have you not presented both
     fitting solutions in this work? What is confusing me is that you mention that this latter
     solution "may correspond more closely to current theoretical ideas". This makes this seem even
     more relevant to present. 
 - Line 630. Use "$\Sigma \pi$" to be consistent with usage elsewhere.

References.
 - You have employed a non-standard format for listing your citations. You have included titles.
   Sometimes you spell out first names and other times you use initials. You give both a journal
   reference and a preprint. Sometimes you list last names first. In many instances you do not
   put proper spacing between abbreviations (e.g. Prog.Part.Nucl.Phys.). Please review this and
   tidy up.
 - Ref. [15] should use "$\Lambda(1405)$" in the title.
 - Ref. [38] should say "Ph.D. thesis".