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

[Mikhail Osipenko]

Dear Authors of pi0 paper,

I am somewhat disappointed by the level of cooperation within our Collaboration. The presented paper makes a claim which is in direct contradiction with published CLAS data from arXiv:0809.1153 [hep-ex]. The two papers use the same data (E1-6), the latter shows good agreement of elastic e-p coincidence cross section (shown in Fig.8), while the former claims 11% correction necessary to recover the same cross section. Although, the two statements are still compatible within systematic errors quoted (10%). A year ago I pointed out this discrepancy at CLAS meeting.

I do believe that the Authors did much better data analysis than I could and clearly the error would be on my side, however the refusal of authors investigating the difference is noteworthy. From my side I was always open to any cross check or benchmark.

Best Regards,
             Mikhail.

My comments:

line 69 - and further use generalized form-factors for consistency,

line 70 - use 1<Q2<10 GeV2, otherwise Q2~1 cannot be treated as a separate kinematic region,

line 77 - you define "q" here and in line 146: these two "q" are different, use different symbols,

Line 77-80 - remove sentence "Since...", as pointless,

line 95-96 - remove ", the LET s-wave..." together with Eq.5,6 - these are repetition of Eqs.2,3 for m_pi=0, trivial,

line 99 - in which "approximation"? Clarify.

lines 103-108 + Eqs.9,10 - all these hve nothing to do with your paper, remove it,

line 123 - use "its violation."

lines 459-467 - entire discussion of RC is awkward, I could not understand what did you mean, please reformulate in simple terms,

line 492 - target of 5 cm was filled with air? Do you have sufficient Z-vertex resolution to isolate target cell walls with +-0.5 cm cuts with <10% precision?

Fig.13 - dashed line in legend is not dashed,

lines 653-654 - Do you want to say here that LCSR has not sigma_TT? Reformulate.