Higher order statistics of curvature perturbations in IFF model and its Planck constraints

We compute the power spectrum P-zeta and non-linear parameters f(NL) and tau(NL) of the curvature perturbation induced during inflation by the electromagnetic fields in the kinetic coupling model (IFF model). By using the observational result of P-zeta, f(NL) and tau(NL) reported by the Planck collaboration, we study the constraint on the model comprehensively. Interestingly, if the single slow-rolling inflaton is responsible for the observed P-zeta the constraint from tau(NL) is most stringent. We also find a general relationship between f(NL), and tau(NL) generated in this model. Even if f(NL) similar to O(1), a detectable tau(NL) can be produced.