On the positivity of MSbar distributions

Abstract: We discuss the positivity of parton distribution functions using the common $\overline{MS}$ factorization scheme. We find that in the perturbative regime $\overline{MS}$ PDFs inherit the strict positivity of physical PDFs. We explicitly discuss the scheme transformation by using suitable physical observables and find that $\overline{MS}$ PDFs are positive above the scale $Q^2$ > 5 GeV^2. Finally, we comment on the direct counterpart of longitudinally polarized PDFs, finding agreement with the unpolarized counterpart.