Search for a WIMP Annihilation Signature in the Core of the Globular Cluster M15

The Whipple 10m Very High Energy gamma-ray telescope has been used to search for indications of WIMP annihilation in the direction of the globular cluster M15. The upper limits derived constrain the amount of super-symmetric dark matter that may reside in globular clusters. Studies of the CMB have accurately determined the density of dark matter (non-baryonic clustering material) in the universe to be ∼ 23% of the total energy density, with most of the remainder being “dark energy” [14]. Weakly interacting massive particles (WIMPs) are an excellent dark matter candidate, especially those arising in super-symmetric extensions to the Standard Model. Such particles can annihilate, and the gamma rays produced should thus trace the dark matter density. The best targets for the search of annihilating dark matter are the most massive dense nearby structures. The Galactic Center is an interesting candidate [16] and is being observed above ∼ 1 TeV with the Whipple telescope [2]. Other galaxies may be of interest as well but their large distances is a strong penalty. Relatively nearby dwarf galaxies [15] have been considered as well as giant galaxies like M87 [1]. With mass to light ratios from 0.5 to 2.5 [12], globular clusters are