Scattering of composite particles in a gauge theory with confinement

Abstract
In order to model positronium-positronium scattering in QED or meson-meson scattering in QCD, we consider QED1+1, which is a gauge theory and confines single fermions. We present first numerical results of a lattice calculation on scattering of two composite particles. The composite particles are taken as neutral, fermion-antifermion, lowest-mass eigenstates of the Hamiltonian. We use the light-cone momentum representation on a lattice and employ a nonperturbative time-dependent method to compute the S matrix.