Spin physics

Abstract

The spin structure of the nucleon is still not very well understood but great progress has been made to understand how much the quark and gluon helicities contribute to the proton spin. In particular recent results from RHIC clearly show a substantial nonzero gluon spin contribution in the accessed x range and the remaining goal is to extend the range down as much as possible - initially with several remaining RHIC measurements and eventually at an EIC. Updated polarized DIS results improved the precision on the quark helicities while single longitudinal spin asymme- tries in the W production of proton-proton collisions indicate an asymmetric, polarized light sea. The transverse spin stucture and exclusive processes opened the way to study the QCD dynamics inside the proton and the hard process, culminating in the prediction of the sign change of the Sivers function when extracted in semi-inclusive DIS and the Drell-Yan(DY) process. While the COMPASS experiment DY measuerments using a pion beam are still being analyzed, first results from the STAR experiment using fully reconstructed W transverse single spin asymmetries in- dicate a preference for a sign-change scenario. Closely related to these DY-type measurements and other transvserse spin measurements is the theoretical progress and need for experimental input in order to quantitatively describe the evolution of objects explicitly depending on instrinsic transverse momentum. In addition several new deeply virtual compton scattering and hard exlu- sive meson production measurements increase the amount of information on generalized parton distribution functions and first, more global, DVCS fits become available.