The General AntiParticle Spectrometer (GAPS) is a novel approach for theindirect dark matter search that exploits cosmic antideuterons. GAPS utilizes adistinctive detection method using atomic X-rays and charged particles from theexotic atom as well as the timing, stopping range and dE/dX energy deposit ofthe incoming particle, which provides excellent antideuteron identification. Inanticipation of a future balloon experiment, an accelerator test was conductedin 2004 and 2005 at KEK, Japan, in order to prove the concept and to preciselymeasure the X-ray yields of antiprotonic exotic atoms formed with differenttarget materials [1]. The X-ray yields of the exotic atoms with Al and Stargets were obtained as ~ 75%, which are higher than were previously assumedin [2]. A simple, but comprehensive cascade model has been developed not onlyto evaluate the measurement results but also to predict the X-ray yields of theexotic atoms formed with any materials in the GAPS instrument. The cascademodel is extendable to any kind of exotic atom (any negatively chargedcascading particles with any target materials), and it was compared andvalidated with other experimental data and cascade models for muonic andantiprotonic exotic atoms. The X-ray yields of the antideuteronic exotic atomsare predicted with a simple cascade model and the sensitivity for the GAPSantideuteron search was estimated for the proposed long duration balloonprogram [3], which suggests that GAPS has a strong potential to detectantideuterons as a dark matter signature. A GAPS prototype flight (pGAPS) waslaunched successfully from the JAXA/ISAS balloon facility in Hokkaido, Japan insummer 2012 [4, 5] and a proposed GAPS science flight is to fly from Antarcticain the austral summer of 2017-2018.
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