The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using $\gamma$-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 $\gamma$-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section $⟨\sigma v⟩$. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach $⟨\sigma v⟩$ values of $6\times {10}^{-26}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ in the $W^{+}{W}^{-}$ channel for a DM particle mass of 1.5 TeV, and $2\times {10}^{-26}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ in the ${\tau }^{+}{\tau }^{-}$ channel for a 1 TeV mass. For the first time, ground-based $\gamma$-ray observations have reached sufficient sensitivity to probe $⟨\sigma v⟩$ values expected from the thermal relic density for TeV DM particles.

• Received 21 March 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.111301