[Clascomment] OPT-IN: Beam Spin Asymmetries in Semi-Inclusive pi0 production

[Paul Stoler]

Hi Colleagues:
This is really a first class work in a very active current subject in our field. There is so much improvement over any previous work. I think that it is definitely  publishable as a PRL. 

One comment. The words in the introduction tend to have a lot of necessary jargon.   There is not much you can to about it in a few page report, and your introductory comments are appropriate. This will be no problem for those readers already fully steeped in the subject and instantly connect the Sivers and Collins affects with pictures in their minds about what they access. However, I believe a simple picture schematically showing an ordinary orbiting quark and how it's L vector relates visually to the electron polarization vector and the transverse momentum will always be helpful for people in our field who are less directly involved with SIDIS measurements or calculations. After all, it can be a very  complicated subject - the structure of the nucleon  (for which  the  euphemism ``rich'' is often applied)