  The presence of additional particles during inflation leads to
non-Gaussianity in late-time correlators of primordial curvature perturbations.
The shape and amplitude of this signal depend on the mass and spin of the extra
particles. Constraints on this distinct form of primordial non-Gaussianity,
therefore, provide a wealth of information on the particle content during
inflation. We investigate the potential of upcoming galaxy surveys in
constraining such a signature through its impact on the observed galaxy power
spectrum. Primordial non-Gaussianity of various shapes induces a
scale-dependent bias on tracers of large-scale structure, such as galaxies.
Using this signature we obtain constraints on massive particles during
inflation, which can have non-zero spins. In particular, we show that the
prospects for constraining particles with spins 0 and 1 are promising, while
constraining particles with spin 2 from power spectrum alone seems challenging.
We show that the multi-tracer technique can significantly improve the
constraints from the power spectrum by at least an order of magnitude.
Furthermore, we analyze the effect of non-linearities due to gravitational
evolution on the forecasted constraints on the masses of the extra particles
and the amplitudes of the imprinted non-Gaussian signal. We find that
gravitational evolution affects the constraints by less than a factor of 2.
