Lower Limits on the Strengths of Gamma Ray Lines from WIMP Dark Matter Annihilation

Abstract

We study the spectra of gamma ray signals that arise from dark matter annihilation in the universe. We focus on the large class of theories where the photon spectrum includes both continuum spectrum of gamma rays that arise from annihilation into Standard Model states at tree level, as well as monochromatic gamma rays arising from annihilation directly into two photons at the one loop level. In this class of theories we obtain lower bounds on the ratio of the strength of the gamma ray line relative to the gamma ray continuum as a function of the dark matter mass and spin. These limits are obtained from the unitarity relation between the tree level amplitude of the primary annihilation channel and the imaginary part of the loop level amplitude for annihilation directly into photons, with the primary decay products running in the loop. These results are exact in the limit that dark matter annihilation is exclusively to a single Standard Model species, occurs through the lowest partial wave and respects CP. Away from this limit the bounds are approximate. Our conclusions agree with the known results in the literature in the case of the Minimal Supersymmetric Standard Model (MSSM). We use the Fermi-LAT observations to translate these limits into upper bounds on the dark matter annihilation cross section into any specific Standard Model state.

11 pages, 3 figures, 1 table ;v2: 14 pages, 6 figures, 2 tables, added discussion of effects of the continuum spectrum in the neighborhood of the line, matches version in PRD

References in corpus (15)

• PYTHIA 6.4 Physics and Manual
• Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope
• The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data
• On The Origin Of The Gamma Rays From The Galactic Center
• Exclusion of canonical WIMPs by the joint analysis of Milky Way dwarfs with Fermi
• Significant Gamma Lines from Inert Higgs Dark Matter
• Constraints on Dark Matter Annihilation in Clusters of Galaxies with the Fermi Large Area Telescope
• Gamma Ray Line Constraints on Effective Theories of Dark Matter
• Singlet Scalar Dark Matter: monochromatic gamma rays and metastable vacua
• Conservative Constraints on Dark Matter Annihilation into Gamma Rays
• The WIMP Forest: Indirect Detection of a Chiral Square
• Indirect detection of light neutralino dark matter in the NMSSM
• Search with EGRET for a Gamma Ray Line from the Galactic Center
• Indirect Detection of Little Higgs Dark Matter
• Loop-induced photon spectral lines from neutralino annihilation in the NMSSM

Cited by in corpus (16)

• Constraining Very Heavy Dark Matter Using Diffuse Backgrounds of Neutrinos and Cascaded Gamma Rays
• Simplified Models vs. Effective Field Theory Approaches in Dark Matter Searches
• Constraining Inert Dark Matter by R_{γγ} and WMAP data
• Bounds on Dark Matter Interactions with Electroweak Gauge Bosons
• Two Lines or Not Two Lines? That is the Question of Gamma Ray Spectra
• Three Exceptions for Thermal Dark Matter with Enhanced Annihilation to Gamma Gamma
• Galaxy Clusters as Reservoirs of Heavy Dark Matter and High-Energy Cosmic Rays: Constraints from Neutrino Observations
• Dark Matter Velocity Spectroscopy
• Diffuse gamma-ray constraints on dark matter revisited. I: the impact of subhalos
• The 130 GeV gamma-ray line and generic dark matter model building constraints from continuum gamma rays, radio and antiproton data
• Entering the Era of Dark Matter Astronomy? Near to Long-Term Forecasts in X-Ray and Gamma-Ray Bands
• Indirect dark-matter detection with MadDM v3.2 -- Lines and Loops
• General calculation of the cross section for dark matter annihilations into two photons
• Lepton-Flavor Violating Mediators
• A Drop in the Pond: The Effect of Rapid Mass Loss on the Dynamics and Interaction Rate of Collisionless Particles
• Constraining Gamma-ray Lines from Dark Matter Annihilation using Fermi-LAT and H.E.S.S. data