7 research outputs found
Wilson Lines off the Light-cone in TMD PDFs
Transverse Momentum Dependent (TMD) parton distribution functions (PDFs) also
take into account the transverse momentum () of the partons. The
-integrated analogues can be linked directly to quark and gluon matrix
elements using the operator product expansion in QCD, involving operators of
definite twist. TMDs also involve operators of higher twist, which are not
suppressed by powers of the hard scale, however. Taking into account gauge
links that no longer are along the light-cone, one finds that new distribution
functions arise. They appear at leading order in the description of azimuthal
asymmetries in high-energy scattering processes. In analogy to the collinear
operator expansion, we define a universal set of TMDs of definite rank and
point out the importance for phenomenology.Comment: 12 pages, presented by the first author at the Light-Cone Conference
2013, May 20-24, 2013, Skiathos, Greece. To be published in Few Body System
Multiparton interactions and multiparton distributions in QCD
After a brief recapitulation of the general interest of parton densities, we
discuss multiple hard interactions and multiparton distributions. We report on
recent theoretical progress in their QCD description, on outstanding conceptual
problems and on possibilities to use multiparton distributions as a laboratory
to test and improve our understanding of hadron structure.Comment: 10 pages, 6 figures. Talk presented at LIGHTCONE 2011, 23-27 May,
2011, Dalla