  Within the so-called cosmological collider program, imprints of new particles
on primordial non-Gaussianities have been studied intensively. In particular,
their non-analytic features in the soft limit provide a smoking gun for new
particles at the inflation scale. While this approach is very powerful to probe
particles of the mass near the Hubble scale, the signal is exponentially
suppressed for heavy particles. In this paper, to enlarge the scope of the
cosmological collider, we explore a new approach to probing spins of heavy
particles from signs of Wilson coefficients of the inflaton effective action
and the corresponding primordial non-Gaussianities. As a first step, we focus
on the regime where the de Sitter conformal symmetry is weakly broken. It is
well known that the leading order effective operator
$(\partial_\mu\phi\partial^\mu\phi)^2$ is universally positive as a consequence
of unitarity. In contrast, we find that the sign of the six derivative operator
$(\nabla_\mu\partial_\nu\phi)^2(\partial_\rho\phi)^2$ is positive for
intermediate heavy scalars, whereas it is negative for intermediate heavy
spinning states. Therefore, under the assumption of tree-level UV completion,
the sign can be used to probe spins of heavy particles generating the effective
interaction. We also study phenomenology of primordial non-Gaussianities
thereof.
