2018/02/28 by Yoshitaka Hatta, Dong-Jing Yang
Physics and Astronomy · #Angular momentum #Angular momentum coupling #Classical mechanics #Gluon #Helicity #High-Energy Particle Collisions Research #Orbital motion #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum electrodynamics #Quark #Spin (aerodynamics) #Total angular momentum quantum number #hep-ph
paper · pdf · doi:10.1016/j.physletb.2018.03.081
12 pages. v2: two figures added, version to appear in Physics Letters B
openalex publication_date 2018/04/04 · arxiv created 2018/04/06 · arxiv updated 2018/04/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We present the numerical solution of the leading order QCD evolution equation for the orbital angular momentum distributions of quarks and gluons and discuss its implications for the nucleon spin sum rule. We observe that at small-x, the gluon helicity and orbital angular momentum distributions are roughly of the same magnitude but with opposite signs, indicating a significant cancellation between them. A similar cancellation occurs also in the quark sector. We explain analytically the reason for this cancellation.