Proton spin after 30 years: what we know and what we don't?

Abstract

More than three decades has passed since the European Muon Collaboration published the first surprising result on the spin structure of the proton. Much theoretical and experimental progress has been made in understanding the origins of the proton spin. In this review, we will discuss what we have learned so far, what are still missing, and what we shall expect to learn from the upcoming experiments including JLab 12 GeV and Electron-Ion Collider. In particular, we focus on first principles calculations and experimental measurements of the total gluon helicity $\Delta G$, and quark and gluon orbital angular momenta.

17 pages, 4 figures, to appear in Nature Review

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Cited by in corpus (6)

• Large-Momentum Effective Theory
• The proton charge radius
• Gluon distributions and their applications to Ioffe-time distributions
• Novel twist-three transverse-spin sum rule for the proton and related generalized parton distributions
• Transverse spin sum rule of the proton
• Neutron Spin Structure from e-3He Scattering with Double Spectator Tagging at the Electron-Ion Collider