Relic density of neutralinos in minimal supergravity

TL;DR

This paper calculates the relic density of neutralinos in the minimal supergravity model, considering all relevant annihilation processes and co-annihilation effects, and identifies parameter regions consistent with observed dark matter.

Contribution

It provides a comprehensive calculation of neutralino relic density including co-annihilation and resonance effects within the mSUGRA framework, highlighting regions with minimal fine-tuning.

Findings

Co-annihilation effects are significant only at the edges of parameter space.

High tan(beta) allows for acceptable relic densities via Higgs resonance annihilation.

Broad regions of parameter space yield correct relic density with little fine-tuning.

Abstract

We evaluate the relic density of neutralinos in the minimal supergravity (mSUGRA) model. All 2->2 neutralino annihilation diagrams, as well as all initial states involving sleptons, charginos, neutralinos and third generation squarks are included. Relativistic thermal averaging of the velocity times cross sections is performed. We find that co-annihilation effects are only important on the edges of the model parameter space, where some amount of fine-tuning is necessary to obtain a reasonable relic density. Alternatively, at high tan(beta), annihilation through the broad Higgs resonances gives rise to an acceptable neutralino relic density over broad regions of parameter space where little or no fine-tuning is needed.