Semi-inclusive deeply inelastic scattering at small qT.

Sivers effect in semi-inclusive deeply inelastic scattering

The Sivers function is extracted from HERMES data on single spin asymmetries in semi-inclusive deeply inelastic scattering. Our analysis use a simple Gaussian model for the distribution of transverse parton momenta, together with the flavor dependence given by the leading 1/Nc approximation and a neglect of the Sivers antiquark distribution. We find that within the errors of the data these appr...

The Status of the Polarized Parton Densities

Deeply inelastic scattering provides a clean way to extract the parton densities of nucleons. After the initial observation that the nucleon spin is not formed by the quarks dominantly [1], detailed measurements of the polarized structure functions followed during the last 20 years. The central question concerns now the parton distribution functions and their scale evolution rather than just th...

Hadronic Final States in Deeply Inelastic Scattering

Results on hadronic final states in deeply inelastic scattering are reviewed. They comprise jet production and its interpretation in perturbative QCD, signatures to distinguish conventional QCD dynamics from possible new features of QCD at small x, and measurements of inclusive charged particle production. Theoretical developments such as color dipole emission and instanton induced final states...

Sivers effect in semi-inclusive DIS and in the Drell-Yan process

The Sivers parton distribution has been predicted to obey a particular “universality relation”, namely to have opposite sign in semi-inclusive deeply inelastic scattering (SIDIS) and the Drell-Yan process. We discuss how, on the basis of present HERMES data, this remarkable prediction of the QCD factorization approach to the description of single spin asymmetries related to the Sivers effect co...

Kinematics of Current Region Fragmentation in Semi-Inclusive Deeply Inelastic Scattering