An analysis of the angular momentum of the proton

We discuss the contributions to the proton helicity in the infinite-momentum frame from polarized quarks (Δq), polarized gluons (ΔG), and orbital angular momentum (L_c). We first examine the behaviour of the polarized structure function g^p₁(x) at small x, arguing that it is consistent with dominance by the a₁(1270) and related Regge trajectories. This supports the EMC estimate of ∫¹₀dxg^p₁(x), and hence the conclusions that Δs<0 and Δu+Δd+Δs{reversed tilde equals}0 . These conclusions are also supported by recent data on elastic ⁽ν⁾p→⁽ν⁾p scattering. Next we argue that in the Skyrme model with only pseudoscalar mesons, ΔG=0 and L_z= 1 2. These results still hold when the chiral lagrangian is made consistent with the scale transformation properties of QCD by incorporating a scalar gluonium field. Finally, we argue on general grounds and by explicit example that if the parameters of the chiral lagrangian are adjusted so that gluons carry ∼ 50% of the proton momentum, most of the orbital angular momentum L_z is carried by quarks.