Gamma Lines without a Continuum: Thermal Models for the Fermi-LAT 130 GeV Gamma Line

Abstract

Recent claims of a line in the Fermi-LAT photon spectrum at 130 GeV are suggestive of dark matter annihilation in the galactic center and other dark matter-dominated regions. If the Fermi feature is indeed due to dark matter annihilation, the best-fit line cross-section, together with the lack of any corresponding excess in continuum photons, poses an interesting puzzle for models of thermal dark matter: the line cross-section is too large to be generated radiatively from open Standard Model annihilation modes, and too small to provide efficient dark matter annihilation in the early universe. We discuss two mechanisms to solve this puzzle and illustrate each with a simple reference model in which the dominant dark matter annihilation channel is photonic final states. The first mechanism we employ is resonant annihilation, which enhances the annihilation cross-section during freezeout and allows for a sufficiently large present-day annihilation cross section. Second, we consider cascade annihilation, with a hierarchy between p-wave and s-wave processes. Both mechanisms require mass near-degeneracies and predict states with masses closely related to the dark matter mass; resonant freezeout in addition requires new charged particles at the TeV scale.

17 pages, 8 figures

References in corpus (25)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope
• Electromagnetic properties of dark matter: dipole moments and charge form factor
• Dark matter constraints from box-shaped gamma-ray features
• How Dark Are Majorana WIMPs? Signals from MiDM and Rayleigh Dark Matter
• Fermi 130 GeV gamma-ray excess and dark matter annihilation in sub-haloes and in the Galactic centre
• Dark Matter Signals from Cascade Annihilations
• Search for heavy long-lived charged particles in pp collisions at sqrt(s) = 7 TeV
• Strong Evidence for Gamma-ray Line Emission from the Inner Galaxy
• Two Lines or Not Two Lines? That is the Question of Gamma Ray Spectra
• The WIMP Forest: Indirect Detection of a Chiral Square
• Three Exceptions for Thermal Dark Matter with Enhanced Annihilation to Gamma Gamma
• Illuminating the 130 GeV Gamma Line with Continuum Photons
• An evidence for indirect detection of dark matter from galaxy clusters in Fermi-LAT data
• Searching for the continuum spectrum photons correlated to the 130 GeV gamma-ray line
• Cold ultrarelativistic pulsar winds as potential sources of galactic gamma-ray lines above 100 GeV
• The PAMELA excess from neutralino annihilation in the NMSSM
• Spectral and spatial variations of the diffuse gamma-ray background in the vicinity of the Galactic plane and possible nature of the feature at 130 GeV
• Double Gamma-ray Lines from Unassociated Fermi-LAT Sources
• Brightening the (130 GeV) Gamma-Ray Line
• Are Lines From Unassociated Gamma-Ray Sources Evidence For Dark Matter Annihilation?
• Gamma Ray Spectra from Dark Matter Annihilation and Decay
• The Dark Knight Falters
• Double gamma-ray lines from unassociated Fermi-LAT sources revisited

Cited by in corpus (30)

• A review of indirect searches for particle dark matter
• Higgs Bosons at 98 and 125 GeV at LEP and the LHC
• 130 GeV gamma-ray line and enhancement of $h\to \gamma \gamma$ in the Higgs triplet model plus a scalar dark matter
• UV Completions of Magnetic Inelastic Dark Matter and RayDM for the Fermi Line(s)
• Two Component Dark Matter : A Possible Explanation of 130 GeV γ-Ray Line from the Galactic Centre
• Gravity-mediated (or Composite) Dark Matter Confronts Astrophysical Data
• Multiple Gamma Lines from Semi-Annihilation
• Neutralino dark matter and the Fermi gamma-ray lines
• Galactic Center Radio Constraints on Gamma-Ray Lines from Dark Matter Annihilation
• Antiprotons from dark matter annihilation through light mediators and a possible excess in AMS-02 $\bar{p}/p$ data
• Gamma-ray lines and One-Loop Continuum from s-channel Dark Matter Annihilations
• Probing Charged Matter Through Higgs Diphoton Decay, Gamma Ray Lines, and EDMs
• Fermi-LAT gamma-ray signal from Earth Limb, systematic detector effects and their implications for the 130 GeV gamma-ray excess
• Looking for new charged states at the LHC: Signatures of Magnetic and Rayleigh Dark Matter
• The 130 GeV gamma-ray line and Sommerfeld enhancements
• Interplay between Fermi gamma-ray lines and collider searches
• From gamma ray line signals of dark matter to the LHC
• A Simple Recipe for the 111 and 128 GeV Lines
• Natural explanation for 130 GeV photon line within vector boson dark matter model
• Gamma Rays from Top-Mediated Dark Matter Annihilations
• Right Sneutrino Dark Matter and a Monochromatic Photon Line
• General calculation of the cross section for dark matter annihilations into two photons
• Indirect dark-matter detection with MadDM v3.2 -- Lines and Loops
• A Clustering Analysis of the Morphology of the 130 GeV Gamma-Ray Feature
• Dichromatic Dark Matter
• Interpretations of the possible 42.7 GeV $\gamma$-ray line
• Dark Matter Annihilation via Breit-Wigner Enhancement with Heavier Mediator
• Axion Portal to Scalar Dark Matter: Unveiling Stabilizing Symmetry Footprints
• Darkonia at Colliders
• 130GeV gamma-ray line through axion conversion