A search for dark matter in the Galactic halo with HAWC

The High Altitude Water Cherenkov (HAWC) gamma-ray observatoryis a wide field-of- view observatorysensitive to 500 GeV - 100 TeV gamma raysand cosmic rays. With its observations over 2/3 of the skyevery day, the HAWC observatoryis sensitive to a wide variety of astrophysical sources, including possible gamma raysfrom dark matter. Dark matterannihilation and decay in the Milky WayGalaxy should produce gamma-raysignals across many degrees on the sky. The HAWC instantaneous field-of- viewof 2 sr enables observations of extended regions on the sky, such as those from dark matterin the Galactic halo. Here we show limits on the dark matterannihilation cross-section and decay lifetime from HAWC observations of the Galactic halowith 15 months of data. These are some of the most robust limits on TeV and PeV dark matter, largely insensitive to the dark mattermorphology. These limits begin to constrain models in which PeV IceCube neutrinos are explained by dark matterwhich primarily decays into hadrons.