Relatore
Stefano Forte
(Istituto Nazionale di Fisica Nucleare)
Descrizione
I discuss the constraints that positivity of physical cross-sections impose on unpolarized and polarized collinear parton distribution functions. I explain why in a generic factorizations scheme leading-twist PDFs may turn negative beyond leading order, and show that however in the commonly used MSbar scheme this cannot happen in the perturbative regime. I then discuss the implications of this for phenomenology, using recent results both in the unpolarized and polarized case.
Autore principale
Stefano Forte
(Istituto Nazionale di Fisica Nucleare)
