[Clascomment] OPT-IN: First Exclusive Measurement of Deep Virtual Compton Scattering off 4 He: Toward the 3D tomography of nuclei

[Volker Burkert]

This is a pioneering measurement and should make a nice PRL. 

Please keep in mind that PRL has tightened their requirements for accepting manuscripts for publication, and they 
have instructed their referees accordingly. It is a good idea to get to their web site and incorporate the requirements
in the manuscript. 


Here are a few minor comments:

Abstract:     
 - ".. the first fully exclusive.." => ".. the first exclusive..." 
 - " A new radial time projection.."    If it is a "novel" design then maybe better "A novel (or unique) type of radial time projection ...".
      If it is just another in a series of RTPC then  "A specially designed time projection .."
 - " ..in a completely model-independent way.." => "in a model-independent way.."

line: 34-35: shorten the sentence to:  " .. and has been the focus of efforts [10-21] at Jefferson Lab, HERA, and CERN." 

line 38: "three-dimensional picture of the nucleon" => "three-dimensional image of the proton" (only the proton has been 
studied with any precision). 

line 40: "giving access to completely new information.." => "giving access to novel information..". 

line 100:  "The experiment E08-024 took place .."  by writing "The experiment E08-024 (CLAS-EG6)took place ..", you 
can define EG6, which is used later in the legend of Figure 6.   

line 109-112: Replace the sentence "The low-energy Moller electrons ....the target" with: 
"The solenoid magnet has two functions; it provides the magnetic field for the momentum analysis in the RTPC, and 
at the same time acts as the guiding field for the low-energy Moller electrons, that are absorbed in a  
heavy shield placed around the beam line."  

line 121: "Kapton straw" => "Kapton tube" or "Kapton cylinder". 

line 159: "The experimental data .... and applied cuts ARE shown in Fig.2" ("data" is plural)

line 207: "distrubution" => distribution. 

line 247-248: "... theoretical calculations by Liuti and Taneja [41]."

line 252: "..but still allow drawing some conclusions".  

line 278: The sentence sounds a bit awkward and the phrase "does not allows to discriminate.." is not good English. 
Maybe better "does not allow discriminating.."  Also, replace "accuracy" with "precision". 

Fig. 5: - CLAS-EG6 in the legend is not defined (it could be defined on page 2 after E08-024). 
          - The Hermes point in the right panel at -t=0.1 overlaps the CLAS point and may perhaps be shifted 
             slightly to larger t for clarity.