Supersymmetric Hybrid Inflation in Light of CMB Experiments and Swampland Conjectures

Abstract: This study revisits supersymmetric (SUSY) hybrid inflation in light of CMB experiments and swampland conjectures. We first show that if one adds radiative, soft mass, and SUGRA corrections to the scalar potential, supersymmetric hybrid inflation is still consistent with Planck 2018 despite an impression that it does not. Usually, in SUSY hybrid inflation with minimal K\"ahler potential, the gauge symmetry breaking scale $M$ turns out to be ${\cal O}(10^{15})$ GeV, which causes proton decay rate problem. In this study, we present a new parameter space where the proton decay rate problem can be avoided by achieving $M$ of the order of $10^{16}$ GeV with $M_{S}^{2}<$0 and $am_{3/2}>$0. In this scenario, one requires a soft SUSY breaking scale $|M_{S}| \gtrsim 10^{6}$ GeV. Moreover, the tensor to scalar ratio $r$ is in the range $10^{-16}$ to $10^{-6}$, which is quite small. In this case, modified swampland hold, but it is difficult to satisfy trans-Planckian censorship conjecture. For this reason, we also consider non-minimal K\"ahler potential. We fixed spectral index $n_{S}=$0.9665 (central value) of Planck 2018 data and $M=2\times 10^{16}$ GeV and present our calculations. We show the canonical measure of primordial gravity waves $r$ for $M_{S}=$ 1 TeV, $m_{3/2}=$ 1 TeV, $\kappa_{S}<0$ for $\cal{N}=$1 and $\cal{N}=$2, ranges from $10^{-5}$ to $0.01$ which can be observed in Planck and next-generation experiments such as LiteBIRD, Simons Observatory, PRISM, PIXIE,CORE, CMB-S4 and CMB-HD experiments that are gearing up to measure it. In addition to it, we present the parametric space and benchmark points for a non-minimal case which is consistent with modified swampland and trans-Planckian censorship conjectures.