  The inflationary universe can be viewed as a "Cosmological Collider" with
energy of Hubble scale, producing very massive particles and recording their
characteristic signals in primordial non-Gaussianities. To utilize this
collider to explore any new physics at very high scales, it is a prerequisite
to understand the background signals from the particle physics Standard Model.
In this paper we describe the Standard Model background of the Cosmological
Collider.
