Galaxy bispectrum from massive spinning particles

Abstract

Massive spinning particles, if present during inflation, lead to a\ndistinctive bispectrum of primordial perturbations, the shape and amplitude of\nwhich depend on the masses and spins of the extra particles. This signal, in\nturn, leaves an imprint in the statistical distribution of galaxies; in\nparticular, as a non-vanishing galaxy bispectrum, which can be used to probe\nthe masses and spins of these particles. In this paper, we present for the\nfirst time a new theoretical template for the bispectrum generated by massive\nspinning particles, valid for a general triangle configuration. We then proceed\nto perform a Fisher-matrix forecast to assess the potential of two\nnext-generation spectroscopic galaxy surveys, EUCLID and DESI, to constrain the\nprimordial non-Gaussianity sourced by these extra particles. We model the\ngalaxy bispectrum using tree-level perturbation theory, accounting for\nredshift-space distortions and the Alcock-Paczynski effect, and forecast\nconstraints on the primordial non-Gaussianity parameters marginalizing over all\nrelevant biases and cosmological parameters. Our results suggest that these\nsurveys would potentially be sensitive to any primordial non-Gaussianity with\nan amplitude larger than $f_{\\rm NL}\\approx 1$, for massive particles with\nspins 2, 3, and 4. Interestingly, if non-Gaussianities are present at that\nlevel, these surveys will be able to infer the masses of these spinning\nparticles to within tens of percent. If detected, this would provide a very\nclear window into the particle content of our Universe during inflation.\n