Aspects of spontaneously broken N = 1 global supersymmetry in the presence of gauge interactions

We discuss models where N=1 global supersymmetry is spontaneously broken, at the classical level, in the presence of non-anomalous gauge interactions. We take such models as effective theories, valid up to some suitable scale and arising from supergravity models with a light gravitino, and therefore we allow them to contain non-renormalizable interactions. First, we examine the case where the goldstino is a gauge singlet. We elucidate the model-independent relations between supersymmetry-breaking masses and some associated interactions, with special attention to the behaviour of some four-particle scattering amplitudes in the high- and low-energy limits. The former gives constraints from tree-level unitarity, the latter affects the phenomenological lower bounds on the gravitino mass. In particular, we give new results for the annihilation of photons into gravitinos, and discuss their implications. We then examine the case with no neutral chiral superfields, so that the goldstino is charged, and the gauge symmetry is also broken. In this context, we discuss the singularity structure and the associated unitarity constraints, relating the scales of supersymmetry and gauge symmetry breaking. We conclude by commenting on possible realistic examples, where the broken gauge symmetry is associated with grand or electroweak unification.