Speaker
Ryskin Mikhail
Description
We consider a few effects which are usually ignored in PDF studies.
- The double counting of the low $k_T
PDF input at $Q=Q_0$. Formally this is a power $Q^2/\mu^2$ correction but
it is non-negligible at moderate scales $\mu$. - The $\epsilon/\epsilon$ contribution generated by the infrared (IR) divergence after the
dimensional regularization. Since the IR divergence is cut off by confinement (or the quark mass)
these terms must be deleted. - The role of the smooth transition through the heavy quark threshold and the
need to work in the Physical scheme where at the NLO (and higher orders) there is no
admixture of the quarks to gluon PDF (and gluons to quark PDF) which occur in the MS-bar scheme.
All these points are not uncertainties, but are real effects which certainly must be accounted for
in global parton analysis.
Primary author
Ryskin Mikhail
