# Heavy Spinning Particles from Signs of Primordial Non-Gaussianities: Beyond the Positivity Bounds

## TL;DR

This paper proposes a novel method to detect the spins of heavy particles during inflation by analyzing the signs of specific operators in the inflaton effective action, extending the reach of cosmological collider techniques beyond near-Hubble-scale particles.

## Contribution

It introduces a new approach to infer the spins of heavy particles from signs of Wilson coefficients in the inflaton effective action, especially for particles heavier than the Hubble scale.

## Key findings

- Sign of the six-derivative operator distinguishes between heavy scalars and spinning states.
- Positive sign for heavy scalars, negative for heavy spinning particles.
- Method extends the scope of primordial non-Gaussianity analysis to heavier particles.

## Abstract

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.