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

[Patrizia Rossi]

First I want to apologize in advance for waiting so long to send my comments on your paper even if they were ready since a while. I saw that now you have already changed the draft and all my comments refer to the first version.
I have read through your manuscript draft for \"Measurement of Single and Double Spin Asymmetries in Deep Inelastic Pion Electroproduction with Longitudinally Polarized Target\" with interest and I think it shows very nice results. My comments are listed below. 

Pag 1 left column:
Here physics motivations for single and double spin asymmetries measurements are given. In my opinion first two paragraphs (\"Measurement of transverse momenta...to be independent of P_T [1]\") and second two paragraphs (\"Azimuthal distributions of final state particles...target [16,17], respectively.\") are not well linked together and there are also some repetitions. For example first 6 lines of the first paragraph and first five of the 2nd one.  Also I think that it is not completely correct the statement that \"Measurement of transverse momenta (P_T) of final state hadrons in semi-inclusive deep inelastic scattering (SIDIS)..., gives access to the transverse momentum distributions ..\". And indeed, the correct statement is in the second paragraph.
Moreover in the second paragraph you talk about \"spin asymmetries\" but you don\'t give any definition of them before. The same it happens in the 3rd paragraph when you talk about \"azimuthal moments\" of the cross section.
So, I think that this part should be re-written in a clearer way and definition of relevant observables should be given.

Pag 1, right column, 2nd par, line 6:
Is it correct to use the word \"measurements\" for lattice calculations?

Pag 2, left column, 4 lines before eq (1):
\"..corrections due to pions coming from rho (from 5 to 20% for z <0.7),..\"
It will be useful to have a small table with the % of pions coming from rho for different z values.

Pag 2, left col, line 4 after eq (1):

\"The contribution from the longitudinal photon (R is the ...fluxes) is accounted for in the depolarization factor D\'(y): eq(2)\"
->\" The contribution from the longitudinal photon ia accounted for in the depolarization factor D\'(y): eq(2)
where R is the ..fluxes.\"

Pag 2, right column, line 3:
\"The dependence of the double spin asymmetry on Bjorken x for..\" -> \"The dependence of the double spin asymmetry on Bjorken x integrated over z ..., P_T ...for..\"
In general: the range of integration of all variables not used in the plots should be always written

Caption Fig 1: 
- A^1(-P) has never been used in the text. Change it with A^1
- \"The solid, dashed ..., respectively.\" -> \"The solid, dashed and dotted curves are calculated using LO GRSV PDF [36] and simple parametrization of the ratio of unfavored and favored fragmentation functions [37] (see text).\"
Then write in the text the parametrization that have been used. 

Pag 2, right column, line 10 from the bottom:
remove (see Fig. 2)

Pag 3, left column, line 3:
\"A fit to A_1(P_T) for pi^+ using the same approach yields a ratio of widths of 0.7..\".
Question: is the value 0.7 the approximation of 0.68 that is reported in the caption? 
If yes why is this value refered only to pi^+ (it should be also for pi^- and pi^0)

Fig 2:
Why do you have only 8 points for A_1 while in the text it is written that there are 9 bins in P_T?

Caption Fig. 3: 
The values of the fit parameters should be removed from the caption and put in the text.


Pag 3, right column, line 11 from the bottom:
\" The kinematic dependence of the ...predictions\"-> \" The kinematic dependence of the ...predictions for x>0.25\".

Pag 4, left column, line 6
\"..with CLAS and a polarized proton target.\" -> \"..with CLAS and a longitudinally  polarized proton target.\"