Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with H.E.S.S.

The inner region of the Milky Way halo harbors a large amount of darkmatter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations ofDM particles using γ-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant γ -ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation crosssection ⟨σv⟩. These constraints are the strongestobtained so far in the TeV DM mass range and improve upon previouslimits by a factor 5. For the Einasto profile, the constraints reach ⟨σv ⟩ values of 6 ×10^-26 cm³ s^-1 in the W+W- channelfor a DM particle mass of 1.5 TeV, and 2 ×10^-26 cm³ s^-1 in the τ⁺τ-channel for a 1 TeV mass. For the first time, ground-based γ-ray observations have reached sufficient sensitivity to probe ⟨σv⟩ values expected from the thermal relic density for TeV DM particles.