https://doi.org/10.1051/epjconf/20158502031
On the role of quark orbital angular momentum in the proton spin
Institute of Physics AS CR, Na Slovance 2, CZ-182 21 Prague 8, Czech Republic
Published online: 23 January 2015
We study the covariant version of the quark-parton model, in which the general rules of the angular momentum composition are accurately taken into account. We demonstrate how these rules affect the relativistic interplay between the quark spins and orbital angular momenta, which collectively contribute to the proton spin. The spin structure functions g1 and g2 corresponding to the many-quark state J = 1/2 are studied and it is shown they satisfy constraints and relations well compatible with the available experimental data including proton spin content Δ∑ ≲ 1/3. The suggested Lorentz invariant 3D approach for calculation of the structure functions is compared with the approach based on the conventional collinear parton model.
© Owned by the authors, published by EDP Sciences, 2015
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