  The squeezed limit of the primordial curvature bispectrum is an extremely
sensitive probe of new physics and encodes information about additional fields
active during inflation such as their masses and spins. In the conventional
setup, additional fields are stable with a positive mass squared, and hence
induce a decreasing signal in the squeezed limit, making a detection
challenging. Here we consider a scalar field that is temporarily unstable by
virtue of a transient tachyonic mass, and we construct models in which it is
embedded consistently within inflation. Assuming IR-finite couplings between
the tachyon and the inflaton, we find an exchange bispectrum with an enhanced
long-short scale coupling that grows in the squeezed limit parametrically
faster than local non-Gaussianity. Our approximately scale-invariant signal can
be thought of as a cosmological tachyon collider. In a sizeable region of
parameter space, the leading constraint on our signal comes from the cross
correlation of $\mu$-type spectral distortions and temperature anisotropies of
the microwave background, whereas temperature and polarization bispectra are
less sensitive probes. By including anisotropic spectral distortions in the
analysis, future experiments such as CMB-S4 will further reduce the allowed
parameter space.
