A Novel Antimatter Detector Based on X-ray Deexcitation of Exotic Atoms

We propose a novel antiparticle detector. The gaseous antiparticle spectrometer (GAPS) effects particle identification through the characteristic X-rays emitted by antiparticles when they form exotic atoms in gases. GAPS obtains particularly high grasp (effective area–solid angle product) at lower particle energies, where conventional schemes are most limited in their utility. The concept is simple and lightweight, so it can be readily employed on balloon and space-based missions. An extremely powerful potential application of GAPS is a space-based search for the neutralino through the detection of a neutralino annihilation by-product – the antideuteron. Paradoxically, this space-based search for the neutralino is capable of achieving comparable sensitivity to as yet unrealized third generation, underground dark matter experiments. And GAPS can obtain this performance in a very modest satellite experiment. GAPS can also provide superior performance in searches for primary antiprotons produced via neutralino annihilation, black hole evaporation and in probing subdominant contributions to the antiproton flux at low energies. In a deep space mission GAPS will obtain higher sensitivity for a given weight and power than BGO calorimeters. Subject headings: cosmic rays — techniques: spectroscopic — dark matter — atomic processes