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

[Volker Burkert]

This is a nice paper, well written. Also, Inna's analysis and comments enhance the physics content significantly. I have a few minor comments:

General: The major result graphs Fig. 14- Fig. 18 should have more prominent symbols. Symbols are too small and should be full not open.  Use full, big circles unless different symbols are used in the same graph.   
Also, when comparing model calculations with data use the same pattern for the same model in different graphs, otherwise it is confusing. As an example, Fig. 13 shows curves from LCSR (dashed), MAID2007 (dotted) and SAID (dash-dotted), while in Fig. 14 and 15 we have LCSR (dashed), MAID2007(dashed-dotted), and SAID (dashed-triple dot).  

Line 204: "..resolution of about 0.6% depending on kinematics". => Give a range for the resolution, e.g. 0.4% - 0.9% depending on kinematics. 

Line 218-221: replace sentence with: "The electron beam energy of 5.754 GeV as determined in this experiment agrees within 6MeV with an independent measurement in Hall A [22]."    


Line 247: "The good electrons ... 0.3." => " Electrons are concentrated near E_tot/p ~0.3. Ideally they should not show any dependence on momentum, albeit a slight momentum dependence is visible in the data.  

Line 274: "For an ideal experiment,.." => "For perfect beam alignment, ..".  

Line 364: " by the red line.." The paper will be printed in b/w and it is better to use patterned lines rather than full lines of different color. "red line could be replaced by a dashed line and referred to as "the dashed red line" , then even color blind on-line readers could identify it. 

Line 375: "blue curve" in Fig.9 could be made blue dashed curve.


Line 395: ".. and W > 1.08 GeV". Should that not be  "..and  W < 1.11 GeV"? 

Line 426: "analyzed similarly to experimental data...." => "analyzed the same way as experimental data.."

Line 472: "Brehmsstrahlung" => "Bremsstrahlung". 

Fig. 10: Can we show more bins in phi*?  In Fig. 12 twice as many bins are shown. 

Line 492/3: "filled with air". In fact, the target was "filled with cold H2 gas".  

Line 499/500: If we say " . approximately 1% depending on the W kinematics" we should give a range, e.g. " 0.5% - 1.5% depending on the W kinematics .." (use correct values).  

Fig. 12: It is not good to show both data sets. Show only the ones corrected with the 11% renormalization factor. Also, use filled symbols not empty ones. 

Line 514: "The discrepancy was not observed in the charge pion - neutron channel". This is misleading. The relevant difference is that elastic cross section in Kijun's analysis is from inclusive elastic scattering ep=>eX, while in this paper from exclusive ep=>ep. The fact that the final states of the physics reactions are different is not relevant, the elastic data were collected together. 


Line 694-696: "The precision of the data in refs. [24,25] near threshold is much smaller than in the present experiment." 
 Why is that the case? It is the same data set. Maybe the binning is bigger, or data start at high W, etc.?? Also note that the elastic cross section comes out better in these analyses than in the present one.

References: Ref. [24], [32] are not listed as CLAS collaboration papers, while others are, e.g. [15],[25],[33]. Make it consistent.