The GAPS Experiment to Search for Dark Matter using Low-energy Antimatter

The GAPS experiment is designed to carry out a sensitive dark mattersearch by measuring low-energy cosmic rayantideuterons and antiprotons. GAPS will provide a new avenue to access a wide range of dark mattermodels and masses that is complementary to direct detection techniques, collider experiments and other indirect detection techniques. Well- motivated theoriesbeyond the Standard Model contain viable dark mattercandidates which could lead to a detectable signal of antideuterons resulting from the annihilation or decay of dark matterparticles. The dark mattercontribution to the antideuteron flux is believed to be especially large at low energies (E < 1 GeV), where the predicted flux from conventional astrophysical sources (i.e. from secondary interactions of cosmic rays) is very low. The GAPS low-energy antiprotonsearch will provide stringent constraints on less than 10 GeV dark matter, will provide the best limits on primordial black holeevaporation on Galactic length scales, and will explore new discovery space in cosmic rayphysics. Unlike other antimattersearch experiments such as BESS and AMS that use magnetic spectrometers, GAPS detects antideuterons and antiprotonsusing an exotic atomtechnique. This technique, and its unique event topology, will give GAPS a nearly background-free detection capability that is critical in a rare-event search. GAPS is designed to carry out its science program using long-duration balloon flights in Antarctica. A prototype instrument was successfully flown from Taiki, Japan in 2012. GAPS has now been approved by NASA to proceed towards the full science instrument, with the possibility of a first long-duration balloon flight in late 2020. Here we motivate low-energy cosmic ray antimattersearches and discuss the current status of the GAPS experiment and the design of the payload.