Induced-Gravity Palatini-like Higgs Inflation in Supergravity Confronts ACT DR6

We formulate within Supergravity a model of induced-gravity inflation, excellently consistent with ACT DR6, inspired by the Palatini gravity. The inflaton belongs in the decomposition of a conjugate pair of Higgs superfields which lead to the spontaneous breaking of a U(1)B−L symmetry at a scale close to the range (0.145–8.35) × 1016 GeV. The inflaton field is canonically normalized thanks to one real and shift-symmetric contribution into the Kähler potential. It also includes two separate holomorphic and antiholomorphic logarithmic terms, the argument of which can be interpreted as the coupling of the inflaton to the Ricci scalar. The attainment of inflation allows for subplanckian inflaton values and energy scales below the cut-off scale of the corresponding effective theory. Embedding the model in a B−L extension of the MSSM we show how the μ parameter can be generated and non-thermal leptogenesis can be successfully realized. An outcome of our scheme is split SUSY with gravitino mass in the range (40–60) PeV, which is consistent with the results of LHC on the Higgs boson mass.