Massive On-Shell Supersymmetric Scattering Amplitudes

We introduce a manifestly little group covariant on-shell superspace for massive particles in four dimensions using the massive spinor helicity formalism. This enables us to construct massive on-shell superfields and fully utilize on-shell symmetry considerations to derive all possible $\mathcal{N}=1$ three-particle amplitudes for particles of spin no greater than one. Throughout, the conceptual and computational simplicity of this approach is exhibited.