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

We study the three-quark light-cone amplitudes of the proton including quarks' 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 Delta(qT)(x, k(perpendicular to)), q(T) (x, k(perpendicular to)), deltaq (x, k(perpendicular to)), and deltaq(L) (x, k(perpendicular to)), twist-three parton distributions g(T) (x) and h(L) (x), helicity-flip generalized parton distributions E(x, xi = 0, Q(2)) and its associates, and the Pauli form factor F-2(Q(2)). (C) 2003 Elsevier Science B.V. All rights reserved.