Light-front wave function of a relativistic composite system in an explicitly solvable model

Abstract The light-front wave function of a composite system, consisting of two scalar particles, interacting by means of massless scalar particle exchange (the Wick-Cutkosky model) is calculated. The wave function obtained concides with that in the Coulomb potential at non-relativistic relative particle momentum, but in the relativistic region depends not only on the relative momentum, but, due to retardation of interaction, also on an additional variable having the form of a unit vector. It is emphasized that for the correct parametrization of the nuclear and hadronic wave functions at relativistic relative momenta, it is necessary to take into account their dependence on this additional variable.