  We propose a new, chiral description for massive higher-spin particles in
four spacetime dimensions, which facilitates the introduction of consistent
interactions. As proof of concept, we formulate three theories, in which
higher-spin matter is coupled to electrodynamics, non-Abelian gauge theory or
gravity. The theories are chiral and have simple Lagrangians, resulting in
Feynman rules analogous to those of massive scalars. Starting from these
Feynman rules, we derive tree-level scattering amplitudes with two higher-spin
matter particles and any number of positive-helicity photons, gluons or
gravitons. The amplitudes reproduce the arbitrary-multiplicity results that
were obtained via on-shell recursion in a parity-conserving setting, and which
chiral and non-chiral theories thus have in common. The presented theories are
currently the only examples of consistent interacting field theories with
massive higher-spin fields.

High Energy Physics - Theory