## A Measurement of Atomic X-ray Yields in Exotic Atoms and Implications for an Antideuteron-Based Dark Matter Search    [PDF]

T. Aramaki, S. K. Chan, W. W. Craig, L. Fabris, F. Gahbauer, C. J. Hailey, J. E. Koglin, N. Madden, K. Mori, H. T. Yu, K. P. Ziock
The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. GAPS utilizes a distinctive detection method using atomic X-rays and charged particles from the exotic atom as well as the timing, stopping range and dE/dX energy deposit of the incoming particle, which provides excellent antideuteron identification. Prior to the future balloon experiment, an accelerator test was conducted in 2004 and 2005 at KEK, Japan, in order to precisely measure the X-ray yields of antiprotonic exotic atoms formed with different target materials. The X-ray yields of the exotic atoms with Al and S targets were obtained as $\sim$ 75%, which are higher than were previously assumed in. A simple, but comprehensive cascade model has been developed not only to evaluate the measurement results but also to predict the X-ray yields of the exotic atoms formed with any materials in the GAPS instrument. The cascade model is extendable to any kind of exotic atom (any negatively charged cascading particles with any target materials), and it was compared and validated with other experimental data and other cascade models for muonic and antiprotonic exotic atoms. The X-ray yields of the antideuteronic exotic atoms are predicted with a simple cascade model and the sensitivity for the GAPS antideuteron search is estimated as 1.3 $\times 10^{-6}$ [m$^{-2}$s$^{-1}$sr$^{-1}$(GeV/n)$^{-1}$] for the proposed long duration balloon program, which suggests that GAPS has a strong potential to detect antideuterons as a dark matter signature. A GAPS prototype flight (pGAPS) was launched successfully from the JAXA/ISAS balloon facility in Hokkaido, Japan in summer 2012 and a proposed GAPS science flight is to fly from Antarctica in the austral summer of 2017-2018.
View original: http://arxiv.org/abs/1303.3871