30TH INTERNATIONAL COSMIC RAY CONFERENCE Antideuterons as an Indirect Dark Matter Signature: Design and Preparation for a Balloon-born GAPS Experiment

The General Antiparticle Spectrometer (GAPS) exploits low energy antideuterons produced in neutralino-neutralino annihilations as an indirect dark matter (DM) signature that is effectively free from background. When an antiparticle is captured by a target material, it forms an exotic atom in an excited state which quickly decays by emitting X-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. The GAPS method of using this combined X-ray and pion signature to uniquely identify antiparticles has been verified through accelerator testing of a prototype detector. We describe the design of a balloon-born GAPS experiment that complements existing and planned direct DM searches as well as other indirect techniques, probing a different, and often unique, region of parameter space in a variety of proposed DM models. We also outline the steps that we are taking to build a GAPS instrument and execute multiple long duration balloon flights. Many extensions to the standard model predict weakly interacting, massive particles (‘WIMPS’) that are stable and thus ideal dark matter (DM) candidates. Underground direct detection experiments detect the nuclear recoil of WIMPS that scatter off target nuclei. WIMPS can also annihilate with other WIMPS in the galactic halo producing various debris such as gamma-rays, neutrinos, positrons, antiprotons and antideuterons. The General Antiparticle Spectrometer (GAPS) is specifically designed to uniquely identify low-energy, low-mass antiparticles which allows us to • execute deep searches for the WIMPS predicted by supersymmetric (SUSY) and universal extra dimension (UED) theories using antideuterons, • search for evaporating primordial black holes using antideuterons, setting the best limits on primordial black hole density, and • perform low energy cosmic-ray antiproton spectroscopy with several orders of magnitude better statistics than current satellite and balloon experiments. The detection rate for antideuterons yields direct information on the particle properties of the DM. When combined with observations from underground experiments, ground-based experiments such as VERITAS, space-based experiments such as GLAST and PAMELA, and accelerator-based experiments, an extremely comprehensive picture of the nature of DM can be obtained. GAPS DARK MATTER EXPERIMENT More than 80 recent papers discuss aspects of antideuteron DM searches. DM searches are highly model dependent, and there are lots of models! To illustrates the key features of a DM search with bGAPS, the antideuteron flux expected from three different benchmark models calculated by Baer and Profumo [?] are plotted in Figure ??. Here, the LSP is associated with SUSY models (mediated primarily by bb̄), and the LKP (Kaluza-Klein) and the LZP (5D Warped GUT) are associated with UED models. These three models are representative of the most popular candidates for DM. GAPS is optimized for operation below 0.3 GeV/n, where the DM signal is largest. Also shown in the plot is the anticipated secondary and tertiary background of antideuterons [?]. Finally, Figure ?? shows the sensitivity to antideuterons for long-duration balloon (LDB) campaigns from Antarctica (60 days total over three flights) and the potential sensitivity from an ultra-long duration balloon (ULDB) flight (300 days total) that might be realized by our projected 2013 launch date. For comparison, the upper limit from the BESS experiment is also plotted. Figure ?? illustrates three important points: 1. GAPS is essentially a background free experiment, 2. GAPS has outstanding DM discovery potential for a wide variety of DM models, and 3. GAPS represents a major improvement over the state of the art. 10-8 10-6 10-4 GAPS LDB BESS limit D F lu x [m -2 s -1 sr -1 G eV -1 ]