Sneutrinos as Mixed Inflaton and Curvaton

Abstract

We investigate a scenario where the supersymmetric partners of two right-handed neutrinos (sneutrinos) work as mixed inflaton and curvaton, motivated by the fact that the curvaton contribution to scalar perturbations can reduce the tensor-to-scalar ratio $r$ so that chaotic inflation models with a quadratic potential are made consistent with the experimental bound on $r$. After confirming that the scenario evades the current bounds on $r$ and the scalar perturbation spectral index $n_s$, we make a prediction on the local non-Gaussianity in bispectrum, $f_{\rm NL}$, and one in trispectrum, $\tau_{\rm NL}$. Remarkably, since the sneutrino decay widths are determined by the neutrino Dirac Yukawa coupling, which can be estimated from the measured active neutrino mass differences in the seesaw model, our scenario has a strong predictive power about local non-Gaussianities, as they heavily depend on the inflaton and curvaton decay rates. Using this fact, we can constrain the sneutrino mass from the experimental bounds on $n_s$, $r$ and $f_{\rm NL}$.