Linking Starobinsky-Type Inflation in no-Scale Supergravity to MSSM

Abstract: A novel realization of the Starobinsky inflationary model within a moderate extension of the Minimal Supersymmetric Standard Model (MSSM) is presented. The proposed superpotential is uniquely determined by applying a continuous R and a Z_2 discrete symmetry, whereas the Kahler potential respects a no-scale-type SU(54,1)/SU(54)x U(1)_R x Z_2 symmetry too. The inflaton is identified with a Higgs-like modulus whose the vacuum expectation value controls the gravitational strength. Thanks to a strong enough coupling (with a parameter cT involved) between the inflaton and the Ricci scalar curvature, inflation can be attained even for subplanckian values of the inflaton with cT>76 and the corresponding effective theory being valid up to the Planck scale. The inflationary observables turn out to be in agreement with the current data and the inflaton mass is predicted to be 3x10^13 GeV. At the cost of a relatively small superpotential coupling constant, the model offers also a resolution to the mu problem of the MSSM. Supplementing MSSM by three right-handed neutrinos we show that spontaneously arising couplings between the inflaton and the particle content of MSSM not only ensure a sufficiently low reheating temperature but also support a scenario of non-thermal leptogenesis consistently with the neutrino oscillation parameters for gravitino heavier than about 10^4 GeV.