From hybrid to quadratic inflation with high-scale supersymmetry breaking

Motivated by the reported discovery of inflationary gravity waves by the BICEP2 experiment, we propose an inflationary scenario in supergravity, based on the standard superpotential used in hybrid inflation. The new model yields a tensor-to-scalar ratio r≃0.14 and scalar spectral index n_s≃0.964, corresponding to quadratic (chaotic) inflation. The important new ingredients are the high-scale, (1.6–10)×10¹³ GeV, soft supersymmetry breaking mass for the gauge singlet inflaton field and a shift symmetry imposed on the Kähler potential. The end of inflation is accompanied, as in the earlier hybrid inflation models, by the breaking of a gauge symmetry at (1.2–7.1)×10¹⁶ GeV, comparable to the grand-unification scale