Anomaly Mediation and Cosmology

TL;DR

This paper presents a supersymmetric model with anomaly mediation and a gauged U(1) symmetry that addresses the slepton problem, enables hybrid inflation with cosmic strings, and impacts dark matter and baryogenesis.

Contribution

It introduces a novel extension of the MSSM with anomaly mediation and a gauged U(1), solving tachyonic slepton issues and linking inflation, cosmic strings, and dark matter.

Findings

The model naturally produces hybrid inflation ending in cosmic strings.

Constraints from CMB data imply a small Higgs mu-term.

Cosmic string decay enhances dark matter relic density.

Abstract

We consider an extension of the MSSM wherein anomaly mediation is the source of supersymmetry breaking, and the tachyonic slepton problem is solved by a gauged U(1) symmetry, which is broken at high energies in a manner preserving supersymmetry, thereby also facilitating the see-saw mechanism for neutrino masses and a natural source for the Higgs mu-term. We show that these favourable outcomes can occur both in the presence and the absence of a large Fayet-Iliopoulos (FI) D-term associated with the new U(1). We explore the cosmological consequences of the model, showing that it naturally produces a period of hybrid inflation, terminating in the production of cosmic strings. In spite of the presence of a U(1) (even with an FI term), inflation is effected by the F-term, with a D-flat tree potential (the FI term, if present, being cancelled by non-zero squark and slepton fields). Calculating the 1-loop corrections to the inflaton potential, we estimate the constraints on the parameters of the model from Cosmic Microwave Background data. We will see that a consequence of these constraints is that the Higgs mu-term necessarily small. We briefly discuss the mechanisms for baryogenesis via conventional leptogenesis, the out-of-equilibrium production of neutrinos from the cosmic strings, or the Affleck-Dine mechanism. Cosmic string decays also boost the relic density of dark matter above the low value normally obtained in AMSB scenarios.