The proton spin: a tale of one-half

by Dr Emanuele R. Nocera (Dipartimento di Fisica dell'Universita' di Genova)

Tuesday 20 Jan 2015, 15:00 → 16:00 Europe/Rome

Dipartimento di Fisica dell'Universita' di Genova

Nucleons, protons and neutrons, are the building blocks of all nuclei, and hence of most of the visible matter in the Universe. They are bound states with spin one-half. Understanding how this is built up from the spin of partons - and their dynamics - is a challenging question in hadron physics, which is still not completely understood. Since the EMC experiment revealed in the late 80s that quark and antiquark spin contributes only a small fraction of the nucleon spin, it was advocated that gluon spin and parton orbital angular momentum should account for its missing part. I review the present status of our knowledge on nucleon spin structure. Specifically, I focus on recent achievements in the determination of spin-dependent parton densities from a global QCD analysis of high-energy scattering data, and I comment on related open issues which will be addressed in the future.

Slides nocera.pdf