Non-thermal Production of Neutralino Cold Dark Matter from Cosmic String Decays

TL;DR

This paper explores how cosmic string decays in certain supersymmetric models can produce neutralino dark matter nonthermally, constraining symmetry breaking scales and neutrino masses to avoid overclosing the universe.

Contribution

It introduces a mechanism for nonthermal neutralino production from cosmic string decays in extended MSSM models, providing new cosmological constraints on symmetry breaking scales and particle masses.

Findings

Cosmic string decay can produce sufficient neutralino dark matter at a symmetry breaking scale of around 10^8 GeV.

To prevent overclosure, the U(1) gauge boson mass must be much larger than the Fermi scale.

The model constrains neutrino masses to be below approximately 30 eV under the see-saw mechanism.

Abstract

We propose a mechanism of nonthermal production of a neutralino cold dark matter particle, $\chi$, from the decay of cosmic strings which form from the spontaneous breaking of a U(1) gauge symmetry, such as $U_{B-L}(1)$, in an extension of the minimal supersymmetric standard model (MSSM). By explicit calculation, we point out that with a symmetry breaking scale $\eta$ of around $10^8$ GeV, the decay of cosmic strings can give rise to $\Omega_\chi \simeq 1$. This gives a new constraint on supersymmetric models. For example, the dark matter produced from strings will overclose the universe if $\eta$ is near the electroweak symmetry breaking scale. To be consistent with $\Omega_\chi \leq 1$, the mass of the new U(1) gauge boson must be much larger than the Fermi scale which makes it unobservable in upcoming accelerator experiments. In a supersymmetric model with an extra $U_{B-L}(1)$ symmetry, the requirement of $\Omega_\chi \leq 1$ puts an upper bound on the neutrino mass of about $30 eV$ provided neutrino masses are generated by the see-saw mechanism.