Talk:Drell–Yan process

AFAIK Drell-Yan can appear not only in nucleon-nucleon collisions, but in hadron-hadron collision.

Quark Flavor Asymmetry
The equation here needs some explanation. What doe in sigma_pd, what do the p and d stand for? What is x-longitudinal momentum fraction? And what does the bar over the u and d represent? It should be explained that these are parton distribution functions and it would help if the pdf page had a similar notation. I'm a particle physics graduate student; if this equation is confusing to me it's probably confusing to most users. Pulu (talk) 15:59, 24 October 2011 (UTC)