  The Galactic Halo is a key target for indirect dark matter detection. The
High Altitude Water Cherenkov (HAWC) observatory is a high-energy (~300 GeV to
>100 TeV) gamma-ray detector located in central Mexico. HAWC operates via the
water Cherenkov technique and has both a wide field of view of 2 sr and a >95%
duty cycle, making it ideal for analyses of highly extended sources. We made
use of these properties of HAWC and a new background-estimation technique
optimized for extended sources to probe a large region of the Galactic Halo for
dark matter signals. With this approach, we set improved constraints on dark
matter annihilation and decay between masses of 10 and 100 TeV. Due to the
large spatial extent of the HAWC field of view, these constraints are robust
against uncertainties in the Galactic dark matter spatial profile.
