[Clascomment] OPT-IN: Measurement of Single and Double Spin Asymmetries in Deep Inelastic Pion Electroproduction with Longitudinally Polarized Target

[Marco Mirazita]

Dear Collegues,
below you can find my comments on the paper

Marco



Pag. 1, introductory part
I think the introductory part should be improved and make more clear. You introduce in one single sentence TMDs and SIDIS. 
Why not first introduce SIDIS generally, then define TMDs of partons (not only quarks), specifying the kinematics regime where the factorization holds, and finally describe what information can be obtained from the single and double spin asymmetries you are presenting.

Pag. 1, left column, paragraph 3
Remove the sentence \", allowing studies .....TMDs.\". k_T-widths are related to the Anselmino\'s gaussian factorization model.

Pag. 2, left column, first paragraph
You should mention here that a direct Collins function measurement has been done by Belle.

Pag. 2, left column, second paragraph, binning description
Many of the binnings described here are not necessary (for example, no z or Q2 dependence are 
presented in the paper). Also, you say that you have 9 bins in P_T up to 1.12, while Fig. 2 shows 
only 8 bins up to 1 GeV. 
Finally, are the cuts on Q^2, W^2 and y mentioned in the right column of pag. 2 when 
you describe Fig. 2 also used for Fig. 1? And are they used also in the SSA calculation?

Pag. 2, Eq. 1
Please unify the notations, the double spin asymmetry is called A_1 here and A^1_p in the caption of 
Fig. 1. Why don\'t use everywhere A_1^h (wehre h stands for the measured hadron)?

Pag. 2, Eq. 2
How has been estimated R?

Pag. 2, Fig. 1
What is the range in z? Is the full range 0.1-0.9 or the same 0.4-0.7 as in Fig. 2?

Pag. 2, right column, second paragraph
The \"different beam energies ...\" you mention here I think refer to difference between CLAS and 
Hermes expeiments. It should be made more clear.

Pag. 2, right column, third column, last sentence
It\'s hard to say that from the data points. You should also discard the last two (maybe last three) data points (is this your definition of the \"moderate p_T\"?). By looking at your data and the curves, you could just say that the agreement for pi- is slightly worse than for pi+ and pi0.

Pag. 2, right column, last paragraph
It\'s hard to follow this part if one doesn\'t read ref. [39]. Just put a sentence or two more, saying that k_T dependence has been factorized and described by a gaussian shape with the gaussian width taken as free parameter. 
You could also keep in Fig. 2 only the curve better fitting the data.

Pag. 3, left column, first paragraph
Is the value 0.7+/-0.1 the same 0.68 mentioned in the caption of Fig. 2? 

Pag. 3, Fig. 2, comparison with Fig. 1
It seems that in Fig. 2 the pi0 data lay between pi+ and pi-, while in Fig. 1 pi0 results almost coincide with pi+ and are higher than pi-. Is this consistent? 

Pag. 3, left column, first paragraph after Fig. 2
What kinematics cuts did you use for SSA? 

Pag. 3, left column, last paragraph
You should mention why you add the cos(\\phi) term in the fitting function and what result you obtained for p3

Pag. 3, Fig. 3
The values of p1 and p2 are your main results on the SSA, so they have to be put in the text, not just in the caption of Fig. 3 (and anyway in a very unreadable way).

Pag. 3, right column, second paragraph
Maybe some more word on the rho would be helpful. Can you estimate the fraction of pi+ and pi- coming from rho decay?