VERITAS Limits on Dark Matter Annihilation in the Galactic Center Halo

Abstract

Well-motivated models of particle dark matter predict its self-annihilation into Standard Model end states, which may be detected by particle detectors or telescopes. We conduct an indirect dark matter search using gamma rays detected by the VERITAS telescope from within $2^\circ$ of the Galactic Center. A template-based approach is used for background estimation, increasing our sensitivity to sources of gamma-ray emission with spatial extents comparable to the $3.5^\circ$ VERITAS field of view. The analysis benefits from data taken exclusively at large zenith angles, which results in an increased effective area at energies above ~1 TeV, compared to small zenith angle observations. No significant gamma-ray signal is observed in the search region, resulting in upper limits on the end-state-dependent dark matter annihilation cross sections. Cross sections as low as $\langle σ_\text{ann} v\rangle = 1.77\times 10^{-25} \text{ cm}^3 \text{ s}^{-1}$ are excluded at 95% confidence assuming complete annihilation into $τ^+ τ^-$, an Einasto profile, and a dark matter mass of 1 TeV.