  We study the imprint of a massive scalar particle on cosmological correlation
functions, and suggest the way to determine the mass of the newly introduced
particle, which is expected to be around 10^14 GeV. After reviewing the basic
theory by Maldacena and the effective field theory (EFT) of inflation by Cheung
et al., we apply these two theories to construct new couplings of a massive
scalar field with primordial fluctuations including an arbitrary number of
gravitons. We compute some correlation functions including these couplings in
the soft-graviton limit. We show that when the number of soft-gravitons is
getting larger, the peak of the correlation function is shifted to larger mass
of the scalar particle. In addition we derive a relation, which relates
correlation functions with N+1 to N soft-gravitons when the mass of the scalar
particle becomes much higher than 10^14 GeV, and confirm the relation by
numerical analysis.
