Relativistic bound states at Born level

Abstract

Theoretical and phenomenological studies indicate that the QCD coupling \alpha_s(Q^2) freezes in the infrared. Hadrons may then be described by a perturbative expansion around states bound only by a confining potential. A linear potential results from the QCD equations of motion when Gauss' law for A^0 is solved with F_{\mu\nu}^a F^{\mu\nu}_a \neq 0 as boundary condition. The \order{\alpha_s^0} Born states are Poincar\'e covariant and can serve as \ket{in} and \bra{out} states of scattering amplitudes. Their Dirac-type wave functions include f\bar f creation/annihilation effects giving sea-like partons at low x_bj.