Three-quark light-cone amplitudes of the proton and quark orbital-motion-dependent observables Original Research Article

We study the three-quark light-cone amplitudes of the proton including quarksʹ transverse momenta. We classify these amplitudes using a newly-developed method in which light-cone wave functions are constructed from a class of light-cone matrix elements. We derive the constraints on the amplitudes from parity and time-reversal symmetries. We use the amplitudes to calculate the physical observables which vanish when the quark orbital angular momentum is absent. These include transverse-momentum dependent parton distributions ΔqT(x,k⊥), qT(x,k⊥), δq(x,k⊥), and δqL(x,k⊥), twist-three parton distributions gT(x) and hL(x), helicity-flip generalized parton distributions E(x,ξ=0,Q2) and its associates, and the Pauli form factor F2(Q2).