  Experiments aiming to directly detect dark matter (DM) particles have yet to
make robust detections, thus underscoring the need for complementary approaches
such as searches for new particles at colliders, and indirect DM searches in
cosmic-ray spectra. Low energy (< 0.25 GeV/n) cosmic-ray antiparticles such as
antideuterons are strong candidates for probing DM models, as the yield of
these particles from DM processes can exceed the astrophysical background by
more than two orders of magnitude. The General Antiparticle Spectrometer
(GAPS), a balloon borne cosmic-ray detector, will perform an ultra-low
background measurement of the cosmic antideuteron flux in the regime < 0.25
GeV/n, which will constrain a wide range of DM models. GAPS will also detect
approximately 1000 antiprotons in an unexplored energy range throughout one
long duration balloon (LDB) flight, which will constrain < 10 GeV DM models and
validate the GAPS detection technique. Unlike magnetic spectrometers, GAPS
relies on the formation of an exotic atom within the tracker in order to
identify antiparticles. The GAPS tracker consists of ten layers of
lithium-drifted silicon detectors which record dE/dx deposits from primary and
nuclear annihilation product tracks, as well as measure the energy of the
exotic atom deexcitation X-rays. A two-layer, plastic scintillator time of
flight (TOF) system surrounds the tracker and measures the particle velocity,
dE/dx deposits, and provides a fast trigger to the tracker. The nuclear
annihilation product multiplicity, deexcitation X-ray energies, TOF, and
stopping depth are all used together to discern between antiparticle species.
This presentation provided an overview of the GAPS experiment, an update on the
construction of the tracker and TOF systems, and a summary of the expected
performance of GAPS in light of the upcoming LDB flight from McMurdo Station,
Antarctica in 2020.
