Massive and massless spin-1 particles with gauge symmetry without Stueckelberg fields

In order to generate mass for an abelian spin-1 vector field while preserving gauge invariance we couple it to a symmetric tensor. The derivative coupling includes up to three derivatives. We show that unitarity, causality and absence of Stueckelberg (compensating) fields single out a unique model up to trivial field redefinitions. The model contains one massive and one massless spin-1 particle. It is shown by means of a master action to be dual to the direct sum of a Maxwell plus a Maxwell-Proca theory.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq