Position Space Interpretation for Generalized Parton Distributions

physical origin for ⊥ distortion
anomalous magnetic moment coupling in Dirac eq:
iκ
2M ¯qσµν qF µν =
↩→
iκ
]
[¯qσ ij qF ij + 2¯qσ 0ν qF 0ν
2M
[
]
κ ⃗σ · ⃗B + (σ × ⃗p) · ⃗E
back
moving spin 1 2
particle with anomalous magnetic moment has
(viewed from observer at rest) transverse electric dipole
moment, which is perp. to both its spin and momentum.
↩→ ⊥ distortion of q(x,b ⊥ ) is consequence of Lorentz invariance
for Dirac particle with anomalous magnetic moment.
Position Space Interpretation for Generalized Parton Distributions – p.54/55