PROPORTIONALLY OFF-MASS-SHELL EQUATION FOR UNEQUAL MASS SYSTEMS

A new two-body relativistic equation is presented. The major advantage of the proposed equation over existing equations in the literature is that this equation automatically adjusts itself for different mass sy stems. Besides unitarity and covariance, this equation gives a physica lly meaningful prescription of how the particles go off-mass-shell in the intermediate states. It allows the particles to go off-mass-shell proportionally to their masses so that when one of the masses becomes infinite, it automatically becomes a one-body equation for the lighter particle and for equal mass systems, it reduces to the Todorov equati on. Because of the off-mass-shell prescription for the intermediate st ates, it will be useful for systems with a wide variety of masses such as mesons, positronium, muonium, pionium, the deuteron and light hadr onic atoms.