Relativistic Quarkonium Model Based on Instantaneous Ladder BS Equation. I: Basic Equation and Its Properties

Since the relativistic effects are not so small even in the charmonium, we investigate a relativistic quark onium model based on the instant ladder BS equation, i.e., the Salpeter equation. The interaction is assumed to be a sum of the linear potential and the gluon exchange propagator in the Coulomb gauge under instantaneous approximation. In this paper we study properties of the Sal peter equation and accumulate kinematical relations. These results will be used in a forthcoming paper in which the mass levels and other properties of the quarkonium predicted by this model will be reported. 1. Introduction