  The presence of massive particles with spin during inflation induces distinct
signatures on correlation functions of primordial curvature fluctuations. In
particular, the bispectrum of primordial perturbations obtains an angular
dependence determined by the spin of the particle, which can be used to set
constraints on the presence of such particles. If these particles are
long-lived on super-Hubble scales, as is the case for example for partially
massless particles, their imprint on correlation functions of curvature
perturbations would be unsuppressed. In this paper, we make a forecast for how
well such angular dependence can be constrained by the upcoming EUCLID
spectroscopic survey via the measurement of galaxy bispectrum.
