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

Understand

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.