Fermi Large Area Telescope Search for Photon Lines from 30 to 200 GeV and Dark Matter Implications

Dark matter (DM) particle annihilation or decay can produce monochromatic $\gamma$ rays readily distinguishable from astrophysical sources. $\gamma$-ray line limits from 30 to 200 GeV obtained from 11 months of Fermi Large Area Space Telescope data from 20–300 GeV are presented using a selection based on requirements for a $\gamma$-ray line analysis, and integrated over most of the sky. We obtain $\gamma$-ray line flux upper limits in the range $0.6–4.5\times {10}^{-9}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, and give corresponding DM annihilation cross-section and decay lifetime limits. Theoretical implications are briefly discussed.