[Clascomment] OPT-IN: Dihadron Azimuthal Correlations in Deep-Inelastic Scattering Off Nuclear Targets

[Volker Burkert]

Dear Adam and Silvia,

Very nice to see that these results have entered the publication stage. 
I have only a few and mostly comments addressing stylistic aspects. 

-- Physical Review mandates that data and lines in figures can be uniquely identified when printed in black&white. In Figure 2, I think the blue and the red points can not be uniquely identified when printed in b/w.  

-- In Fig.4 the data are partially overlapping the text in the figures, which should be avoided. 

-- Fig. 6 The blue and red colors don't really help here. How the uniqueness is preserved is that in the caption u is accociated with red, and d is associated with blue, both of which appear in the figure legend. The color then not be needed and b/w may just do it, with the distinguishing fact be that one is widely shaded the other one densely shaded (or something similar). 

-- In Fig.5 the colors could also be avoided since the curves are identified by their patterns.  

-- line 67: "the amplitude from BH can be accurately computed". For the proton that is so because of the accurate measurements of the  elastic e.m. formfactors that are used as input to the calculations. Is the same true for the neutron?  

-- line 85: "out worldwide". It may be sufficient to just list the laboratories.  

-- line 131: "40 x 10^9" triggers. Maybe be in addition (or instead) give the integrated luminosity in fb^(-1).  

-- line 201/202: Avoid referring in the text to the colors in a the figures. This belongs into the caption.   

-- Thoughout the discussion on page 4 there is reference to a mix of GPDs and CFFs. GPDs are real quantities and are identified as E or H, while CFFs are complex quantities and written as Re(\mathcal{H}) and Im(\mathcal{E}).  So the example on line 288 "imaginary part of E" 
should be avoided. I suggest to avoid, if possible, the use of GPDs other than in the general discussion in the beginning and where they are used to relate GPDs to the CFFs. 

Best
Volker