Constraining Gravitino Dark Matter with the Cosmic Microwave Background

Abstract

We consider super-gravity models in which the lightest supersymmetric particle (LSP) is a stable gravitino. The next-to-lightest supersymmetric particle (NLSP) freezes out with its thermal relic density and then decays after $(10^5-10^{10})$ sec, injecting high-energy photons into the cosmic plasma. These photons heat up the electron plasma which then thermalizes with the cosmic microwave background (CMB) via Compton scattering, bremsstrahlung and double-Compton scattering. Contrary to previous studies which assume instantaneous energy injection, we solve the full kinetic equation for the photon number density with a source term describing the decay of the NLSP. This source term is based on the requirement that the injected energy be almost instantaneously redistributed by Compton scattering, hence leading to a time-dependent chemical potential. We investigate the case of a stau NLSP and determine the constraints on the gravitino and stau masses from observations of the CMB spectrum by assuming that all gravitino LSPs come from stau NLSP decays. Unlike the analytical approximations, we find that there may be a stau mass below which the constraint from the CMB spectrum vanishes.

8 pages, 6 figures, revtex4, replaced to match published version

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• Gravitino Dark Matter and Cosmological Constraints
• Quasinormal modes of gravitational perturbation around a Schwarzschild black hole surrounded by quintessence
• Dark Matter Candidates - Axions, Neutralinos, Gravitinos, and Axinos
• Gravitino Dark Matter in the CMSSM With Improved Constraints from BBN
• Green's function of the cosmological thermalization problem II: effect of photon injection and constraints
• The number density of a charged relic
• Massive Charged Scalar Quasinormal Modes of Reissner-Nördstrom Black Hole Surrounded by Quintessence
• Dark matter from late decays and the small-scale structure problems
• Dark Matter from Gaugino Mediation
• A Re-analysis of Gravitino Dark Matter in the Constrained MSSM
• Minimal Supergravity with m_0^2 < 0
• Gravitino LSP and leptogenesis after the first LHC results
• The Gravitino-Stau Scenario after Catalyzed BBN
• Geodesic Structure of the Quantum-Corrected Schwarzschild Black Hole Surrounded by Quintessence
• Thermodynamics of Schwarzschild black hole surrounded by quintessence in gravity's rainbow
• Constraints on Gravitino Decay and the Scale of Inflation using CMB spectral distortions
• Massive scalar field quasinormal modes of a Schwarzschild black hole surrounded by quintessence
• Stop Decay with LSP Gravitino in the final state: ${\tilde{t}}_1\to \tilde{G}Wb$