Non-Gaussianity as a Particle Detector
  We study the imprints of massive particles with spin on cosmological
correlators. Using the framework of the effective field theory of inflation, we
classify the couplings of these particles to the Goldstone boson of broken time
translations and the graviton. We show that it is possible to generate
observable non-Gaussianity within the regime of validity of the effective
theory, as long as the masses of the particles are close to the Hubble scale
and their interactions break the approximate conformal symmetry of the
inflationary background. We derive explicit shape functions for the scalar and
tensor bispectra that can serve as templates for future observational searches.
