Two-field inflation with non-minimal coupling

Motivated by the recent 'Higgs-inflation' scenario based on a single inflaton field, we consider more generic two-field inflation with non-minimal (NM) coupling term. The generic analytic expressions are derived for cosmological observables with the product-separable as well as additive-separable potentials when the NM coupling term is dominated by one of the two fields. A hybrid model of the inflaton potential with a NM coupling , which guarantees the flatness, is closely examined as a concrete example. Compared to the minimal model with K = 0, the NM model is shown to provide better fit to the recent cosmological observation by WMAP9 and Planck2013 with the relatively lower field values during the inflationary epoch. Most interestingly, a small value of tensor-to-scalar ratio requires a large NM coupling in our scenario. The model produces non-observably small non-Gaussianity (NG) in most of parameter space while a large NG is obtainable only when the inflation takes place in a limited field space along the top of the potential.