[Clascomment] OPT-IN:First Measurement of Deeply Virtual Compton Scattering on the Neutron with Detection of the Active Neutron

[Steffen Strauch]

Dear Adam and Silvia,

I have a brief comment about your definition of beam-spin asymmetry:

You define in line 91 the acronym BSA for the beam-spin asymmetry. Typesetting this in equations is a bit awkward.  In Eq. (4), you put BSA in text mode.  In Eq. (5), it is given in italic but it looks like the product of three quantities, B, S, and A.  Ideally, there is a single symbol for the physical quantity.  

I would recommend following previous precedents and labeling the beam-spin asymmetry with A_{LU}.  Equation (3) in A. Airapetian, Phys.Rev.Lett.87:182001,2001 (your Ref. [22]) defines A_{LU} in the same way as you do BSA in Eq. (5) of your paper.  Using A_{LU} for the beam-spin asymmetry is consistent with the caption of your Fig. 4. You state in the caption that the beam-spin asymmetry is shown as a function of phi, and the y-axis is labeled A_{LU}.  If you want to stick with BSA for the beam-spin asymmetry, the axis should be labeled with BSA. 

For some parts of your paper, you use A_{LU} for the “amplitude of the \sin\phi fits to the BSA”.  Isn’t that the quantity that Ref. [22] labels as A_{LU}^{\sin\phi}?  

And a minor point: Line 53 defines x as the average parton momentum.  Is x not a momentum fraction?

All the best,

Steffen