Transverse spin observables in hard-scattering hadronic processes within collinear factorization

We review what is currently known about the transverse spin structure of hadrons, in particular from observables that can be analyzed within a collinear framework. These effects have been around for 40 years and represent a critical test of perturbative QCD. We look at both proton–proton and lepton–nucleon collisions for various final states. While the main focus is on transverse single-spin asymmetries, we also discuss how longitudinal-transverse double-spin asymmetries offer a complimentary, yet equally important, source of information on the quark–gluon content of hadrons. We also summarize some recent progress in solidifying the theoretical formalism behind these observables and give an outlook on future directions of research.

Nucleon Partonic Spin Structure to be Explored by the Unpolarized Drell-Yan Program of COMPASS Experiment at CERN

The observation of the violation of Lam-Tung relation in the [Formula: see text] Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.

Transverse Spin Structure Function

The transverse spin-dependent nucleon structure function at large is computed within the Wandzura-Wilczek relation, using NLO fit. Also we investigate the twist-3 contribution of via calculating . It turns out that although the twist-3 part of can be negligible for DIS processes, it has a significant value in resonance region.