  We explore the possibility to make use of cosmological data to look for
signatures of unknown heavy particles whose masses are on the order of the
Hubble parameter during the time of inflation. To be more specific we take up
the quasi-single field inflation model, in which the isocurvaton $\sigma $ is
supposed to be the heavy particle. We study correlation functions involving
both scalar ($\zeta $) and tensor ($\gamma $) perturbations and search for
imprints of the $\sigma$-particle effects. We make use of the technique of the
effective field theory for inflation to derive the $\zeta \sigma $ and $\gamma
\zeta \sigma $ couplings. With these couplings we compute the effects due to
$\sigma $ to the power spectrum $\langle \zeta \zeta \rangle $ and correlations
$\langle \gamma^{s} \zeta \zeta \rangle$ and $\langle \gamma^{s_{1}} \gamma
^{s_{2}} \zeta \zeta \rangle $, where $s$, $s_{1}$ and $s_{2}$ are the
polarization indices of gravitons. Numerical analyses of the $\sigma$-mass
effects to these corrlations are presented. It is argued that future precise
observations of these correlations could make it possible to measure the
$\sigma$-mass and the strength of the $\zeta \sigma$ and $\gamma \zeta \sigma$
couplings. As an extension to the $N$-graviton case we also compute the
correlations $\langle \gamma ^{s_{1}} \cdots \gamma ^{s_{N}} \zeta \zeta
\rangle $ and $\langle \gamma ^{s_{1}} \cdots \cdots \gamma ^{s_{2N}} \zeta
\zeta \rangle $ and their $\sigma$-mass effects. It is suggested that larger
$N$ correlation functions are useful to probe larger $\sigma$-mass .
