  The Large-Scale Structure (LSS) of the universe has the potential to provide
decisive answers to the remaining open questions in cosmology. Early attempts
at modelling it analytically focused on using perturbation theory. However,
small-scale effects introduced by gravitational collapse cannot be described
perturbatively and this failure of perturbation theory is reflected even on the
largest scales. The Effective Field Theory of Large Scale Structure (EFTofLSS)
has emerged as a consistent method for describing LSS on large scales by
introducing counterterms that account for the effects of small-scale dynamics.
So far studies of the EFT have mostly focused on the two and three point
functions with little attention devoted to the four point function or
trispectrum. The trispectrum probes cubic interactions arising from non-linear
clustering, biasing, and primordial non-Gaussianities, and constitutes a key
element of the covariance matrix of the power spectrum. In this paper, we
present explicit calibrations of the EFT counterterms for the one-loop
trispectrum. Specifically, we find clear evidence for non-zero EFT corrections.
We define two one-parameter ans\"{a}tze for the counterterm of the one-loop
propagator and show that they provide a good correction to the residual at
scales below k~0.07 h/Mpc. We then take the amplitudes of the linear and
quadratic counterkernels calculated in our previous paper on the bispectrum and
use them in the remaining counterterms, establishing consistency of the
counterterms in the two, three and four point function. We also show that the
commonly used EdS approximation for the growth of the density fields leads to
errors that are of the same magnitude as loop corrections to the trispectrum on
large scales.
