Neutralino annihilation in the Galactic center

Current astrophysical data indicate the need for a cold dark matter component with $\Omega \approx 0.3$ (see [Gawiser & Silk 1998]; [Primack 1998]; [Kamionkowski 1998]). A good candidate for this component is the neutralino, the lightest stable supersymmetric particle. If neutralinos do comprise the dark matter and are concentrated near the center of our galaxy, their direct annihilation to gamma-rays should produce a unique signal not easily mimicked by other astrophysical processes: a monoenergetic annihilation line with mean energy equal to the neutralino mass. Cosmological constraints and limits from accelerator experiments restrict the neutralino mass to the range 30GeV - 3TeV. Thus, VERITAS and GLAST together will allow a sensitive search over the entire allowed neutralino mass range. Recent estimates of the annihilation line flux for neutralinos at the galactic center (Bergström, Ullio & Buckley 1998) using a galactic model with central cusps in the density distribution of the dark matter halos (Navarro, Frenk & White 1996) predict a gamma-ray signal which may be of sufficient intensity to be detected with VERITAS (Figure 9) and GLAST. The better sensitivity and lower energy threshold of VERITAS will be critical to covering a broad part of the allowed range of neutralino and dark matter parameters.

  

Figure 9: Neutralino annihilation rate from the Galactic center. Shown are the sensitivity curves for Whipple, the Granite III upgrade of the Whipple telescope, and VERITAS. Each point represents a particular choice of supersymmetry model parameters in the experimentally allowed range. Figure from Bergström et al. (1998).