Section on Prospects for Dark Matter Detection of the White Paper on the Status and Future of Ground-Based TeV Gamma-Ray Astronomy

This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the charac- teristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos.

Pre-launch estimates for GLAST sensitivity to Dark Matter annihilation signals

We investigate the sensitivity of the Gamma-ray Large Area Space Telescope (GLAST) to indirectly detect weakly interacting massive particles (WIMPs) through the $gamma$-ray signal that their pair annihilation produces. WIMPs are among the favorite candidates to explain the compelling evidence that about 80% of the mass in the Universe is non-baryonic dark matter (DM). They are serendipitously motivated by various extensions of the standard model of particle physics such as Supersymmetry and Universal Extra Dimensions (UED). With its unprecedented sensitivity and its very large energy range (20 MeV to more than 300 GeV) the main instrument on board the GLAST satellite, the Large Area Telescope (LAT), will open a new window of discovery. As our estimates show, the LAT will be able to detect an indirect DM signature for a large class of WIMP models given a cuspy profile for the DM distribution. Using the current state of the art Monte Carlo and event reconstruction software developed within the LAT collaboration, we present preliminary sensitivity studies for several possible sources inside and outside the Galaxy. We also discuss the potential of the LAT to detect UED via the electron/positron channel. Diffuse background modeling and other background issues that will be important in setting limits or seeing a signal are presented.

Dark Matter Annihilation in Substructures Revised

Upcoming $gamma$-ray satellites will search for Dark Matter annihilations in Milky Way substructures (or clumps). The prospects for detecting these objects strongly depend on the assumptions made on the distribution of Dark Matter in substructures, and on the distribution of substructures in the Milky Way halo. By adopting simplified, yet rather extreme, prescriptions for these quantities, we compute the number of sources that can be detected with upcoming experiments such as GLAST, and show that, for the most optimistic particle physics setup ($m_chi=40$ GeV and annihilation cross section $sigma v = 3 times 10^{-26}$ cm$^3$ s$^{-1}$), the result ranges from zero to $sim$ hundred sources, all with mass above $10^{5}Modot$. However, for a fiducial DM candidate with mass $m_chi=100$ GeV and $sigma v = 10^{-26}$ cm$^3$ s$^{-1}$, at most a handful of large mass substructures can be detected at $5 sigma$, with a 1-year exposure time, by a GLAST-like experiment. Scenarios where micro-clumps (i.e. clumps with mass as small as $10^{-6}Modot$) can be detected are severely constrained by the diffuse $gamma$-ray background detected by EGRET.