Interactions of a Single Goldstino

The single goldstino interaction is given by the goldstino derivative coupling to the supercurrent. In an alternative description, the goldstino couples nonderivatively. We give a simple method to establish the equivalence of the two approaches, valid to all orders in perturbation theory, and for any scattering process involving an arbitrary number of particles, but with a single external goldstino. In the meantime, we find in the nonderivative form of the goldstino interaction a new quartic vertex that has been overlooked, and terms that were included incorrectly in the literature. The phenomenological implication of this new quartic operator is discussed.