Non-Gaussianity from $X, Y$ gauge bosons in Cosmological Collider
  Physics
  Heavy fields of Hubble scale order present during inflation contribute to the
non-Gaussian signature for the three-point function of the inflaton. Taking
into account that Hubble scale is around the scale of grand unified theory
(GUT), this opens a possibility that the GUT scale signatures, which are very
hard to be discovered at collider, might be detectable by using information
from the precise observations of cosmic microwave background. We discuss a
detactability of the $X, Y$ gauge boson present in any GUT in a framework of
cosmological collider physics. Calculating one-loop contributions of $X, Y$
gauge bosons to the inflaton three-point functions, we find a remarkable result
that one-loop diagram with interactions originated from the mass terms of $X,
Y$ gauge bosons provides an enhancement factor expressed by the ratio between
the $X, Y$ gauge boson mass and Hubble scale as $(m_X/H)^4$. In an estimation
of the non-Gaussianity, this factor is crucial and its impact on the
detactability of $X, Y$ gauge bosons is discussed.
