[Clascomment] OPT-IN: First multidimensional, high precision measurements of semi-inclusive pi+ beam single spin asymmetries from the proton over a wide range of kinematics

[Sebastian Kuhn]

Overall a very nice paper. Some of the discussion could be streamlined and shortened - e.g., the text at the beginning of col 2, p. 2 is somewhat redundant with that below Eq. 3. Similarly, the intricacies of the models 1-3 are described at the end of p.3 and then again in the 2nd column of p.4. I am also not sure that having 3 different Figs. displaying the 4-dimensional binning (and detailed descriptions of what can be seen in each of them) adds much to the impact. I probably would leave out Fig. 7 entirely. Instead, can you give a quantitative criterion why you think model 2 describes the data best?

This should make a little more room for experimental details. For one of the 1st 2 path-blazing experiments with CLAS12, it would have been nice to get a more detailed description, e.g., how e' and pi+ are selected (including corresponding plots of EC, ToF or similar signals). Similarly, a bit more detail on how we know the systematic uncertainties from, e.g., kaon contamination or radiative effects would be much appreciated (including numerical estimates of their individual contributions). You don't say anything about MC simulation, acceptance and bin migration effects, etc. 

Some minor issues: The "circles" vs. "squares" in Fig. 2 are too small to easily distinguish (maybe use triangles and circles?). In 2 places, the future "will" is used when referring to the paper itself - I'd just stay with present tense. There are a few more minor suggestions which are in my edited version of the paper (to be sent separately to the authors) - without line numbers, it would be difficult to describe them.