Relation between transverse momentum dependent distribution functions and parton distribution functions in the covariant parton model approach

Non-universality of transverse momentum dependent parton distribution functions

In the field theoretical description of hadronic scattering processes, single transverse-spin asymmetries arise due to gluon initial and final state interactions. These interactions lead to process dependent Wilson lines in the operator definitions of transverse momentum dependent parton distribution functions. In particular for hadron–hadron scattering processes with hadronic final states this...

Renormalization-group approach to transverse-momentum dependent parton distribution functions in QCD

We discuss the renormalization of gauge-invariant transverse-momentum dependent (TMD), i.e., unintegrated, parton distribution functions (PDFs) and carry out the calculation of their anomalous dimension at one loop. We show that in the light-cone gauge, TMD PDFs contain UV divergences that may be attributed to the renormalization effect on a cusp-like junction point of the gauge contours at inf...

Gauge Invariance and Renormalization-group Effects in Transverse-momentum Dependent Parton Distribution Functions

A range of issues pertaining to the use of Wilson lines in integrated and transversemomentum dependent (TMD) parton distribution functions (PDF) is discussed. The relation between gauge invariance and the renormalization properties of the Wilson-line integrals is given particular attention. Using an anomalous-dimensions based analysis in the light-cone gauge, a generalized definition of the TMD...

Parton Distribution Functions

Dynamical parton distribution functions

Recent measurements for F2(x, Q ) have been analyzed in terms of the ‘dynamical’ and ‘standard’ parton model approach at NLO and NNLO of perturbative QCD. Having fixed the relevant NLO and NNLO parton distributions, the implications and predictions for the longitudinal structure function FL(x,Q ) are presented. It is shown that the previously noted extreme perturbative NNLO/NLO instability of F...