2021/11/30 by S. Bürger, Thomas Wurm, T. Wurm +11
Mathematics · Physics and Astronomy · #Chiral perturbation theory #Geometry #High-Energy Particle Collisions Research #Lattice (music) #Lattice QCD #Lattice field theory #Mathematical physics #Mathematics #Nucleon #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quark #Twist #hep-lat #hep-ph
paper · pdf · doi:10.1103/physrevd.105.054504
17 pages, 8 figures; v2: 1 figure, 1 reference and a few clarifications added, analysis corrected, results slightly changed
openalex publication_date 2022/03/08 · arxiv created 2022/03/09 · arxiv updated 2022/03/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Using lattice QCD, we calculate the twist-2 contribution a2 to the third Mellin moment of the spin structure functions g1 and g2 in the nucleon. In addition we evaluate the twist-3 contribution d2. Our computations make use of Nf=2+1 gauge field ensembles generated by the Coordinated Lattice Simulations (CLS) effort. Neglecting quark-line disconnected contributions we obtain as our best estimates a2(p)= 0.069(17), d2(p)= 0.0105(68) and a2(n)= 0.0068(88), d2(n)= -0.0009(70) for the proton and the neutron, respectively, where we use the normalizations given in Eqs. (58) and (59). While the a2 results have been converted to the MS scheme using three-loop perturbation theory, the numbers for d2 are given in the regularization independent momentum subtraction (RI^′-MOM) scheme, i.e., the conversion has been performed only in tree-level perturbation theory. The d2 results can be interpreted as corresponding to a transverse color Lorentz force on a quark in a transversely polarized proton of size F(u) = 116(61) MeV/fm and F(d) = -38(66) MeV/fm for u and d quarks, respectively. The error estimates quoted include statistical and systematic uncertainties added in quadrature.