Hybrid inflation from supersymmetry breaking

TL;DR

This work extends the framework of inflation by supersymmetry breaking to a hybrid inflation setting by incorporating a waterfall field, enabling a parametric separation between the inflation scale and the supersymmetry-breaking scale while preserving the inflationary predictions. The model identifies the inflaton with the superpartner of the goldstino under a gauged U(1)_R, and uses higher-order corrections to the inflaton Kähler potential to generate naturally small slow-roll parameters; a waterfall sector then ends inflation and tunes the vacuum energy with a controllable δ^2 parameter. The analysis demonstrates that a perturbative global vacuum describing low-energy SM physics can be studied within a region of parameter space, with the SUSY-breaking scale largely decoupled from inflation and a light spectrum that contains the inflaton sector (U(1)_R gauge boson and gaugino) near the inflation scale. A concrete benchmark in Model 2 shows a multi-TeV to tens-of-TeV spectrum, including a bino-like LSP, while the waterfall sector remains superheavy, yielding a distinctive experimental signature for this inflationary scenario.

Abstract

We extend a recently proposed framework, dubbed inflation by supersymmetry breaking, to hybrid inflation by introducing a waterfall field that allows to decouple the supersymmetry breaking scale in the observable sector from the inflation scale, while keeping intact the inflation sector and its successful predictions: naturally small slow-roll parameters, small field initial conditions and absence of the pseudo-scalar companion of the inflaton, in terms of one free parameter which is the first order correction to the inflaton Kähler potential. During inflation, supersymmetry is spontaneously broken with the inflaton being the superpartner of the goldstino, together with a massive vector that gauges the R-symmetry. Inflation arises around the maximum of the scalar potential at the origin where R-symmetry is unbroken. Moreover, a nearby minimum with tuneable vacuum energy can be accommodated by introducing a second order correction to the Kähler potential. The inflaton sector can also play the role of the supersymmetry breaking 'hidden' sector when coupled to the (supersymmetric) Standard Model, predicting a superheavy superparticle spectrum near the inflation scale. Here we show that the introduction of a waterfall field provides a natural way to end inflation and allows for a scale separation between supersymmetry breaking and inflation. Moreover, the study of the global vacuum describing low energy Standard Model physics can be done in a perturbative way within a region of the parameter space of the model.

Figures (4)

• Figure 1: Inflation followed by waterfall. The figure in the bubble magnifies the detailed shape of the potential during the inflation, which is a shallow valley. ${\varphi}_s^\pm$ and ${\varphi}_0$ will be introduced explicitly in Section \ref{['subsec:Vrho0']}. The real part $\phi_R$ is suppressed because the potential is stable in this direction and the trajectory always runs with $\phi_R=0$.
• Figure 2: Structure of the F-term potential with $\rho=0$ is given for the cases $\mu>2z$ and $\mu<2z$. The potential is stable (minimum) at $\phi_R=0$ in both cases. Only ${\varphi}$-axis (the imaginary axis) is shown. The region ${\varphi}>z^{-1/2}$ is not drawn because the Kähler metric becomes negative.
• Figure 3: Potential at $\rho$ slices in the case $\mu>2z$.
• Figure 4: