Three-Quark Light-Cone Amplitudes of The Proton And Quark-Orbital-Motion Dependent Observables

Abstract

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 $\Delta q_T(x, k_\perp)$, $q_T(x, k_\perp)$, $\delta q(x, k_\perp)$, and $\delta q_L(x,k_\perp)$, 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 $F_2(Q^2)$.