Gravitino phenomenology and cosmological implications of supergravity

TL;DR

This paper investigates gravitino production during the early universe, analyzing supergravity interactions, unitarity issues at high energies, and the potential of gravitinos as dark matter within a gauge mediation framework.

Contribution

It provides a detailed analysis of gravitino production mechanisms, unitarity breaking in supergravity interactions, and proposes a model where low-temperature reheating can still produce sufficient gravitino dark matter.

Findings

Supergravity vertices lead to unitarity breaking at high energies.

Longitudinal W boson polarizations become strongly interacting at high energies.

Gravitino dark matter can be produced with low reheating temperatures in gauge mediation models.

Abstract

Gravitino production in the primordial Universe is investigated into details. After briefly reviewing inflation, supersymmetry and supergravity, we first study the scattering of massive W bosons in the thermal bath of particles, during the period of reheating. It is found that the process generates in the cross section terms which eventually lead to unitarity breaking above a certain scale. This happens by virtue of the supergravity vertex. We show that the longitudinal polarizations of the on-shell W become strongly interacting in the high energy limit, and that the inclusion of diagrams with off-shell scalars of the MSSM does not cancel the divergences. Next, we consider the dynamics and the decay into gravitinos of a scalar field S, which starts oscillating in its potential at the end of inflation. We embed S in a model of gauge mediation with metastable vacua, where the hidden sector is of the O'Raifeartaigh type. By demanding that the gravitinos thus produced provide with the observed Cold Dark Matter density, we modify previous results in the literature, and find that it is easy to account for gravitino Dark Matter with an arbitrarily low reheating temperature.