GAPS (General AntiParticle Spectrometer) is a balloon-borne large-acceptance experiment de-
signed to detect low-energy (< 0.25 GeV/n) cosmic-ray antinuclei during three ∼35-day Antarctic
flights, the first of these planned for the 2024-2025 austral summer. The GAPS apparatus, cur-
rently in preparation for the first flight, consists of a tracker equipped with large-area lithium-drifted
silicon detectors and surrounded by a large-acceptance time-of-flight system made of plastic scin-
tillators. This design has been optimized to perform a novel antiparticle identification technique
based on an antinucleus capture and the subsequent exotic atom formation and decay, allowing
more active target material and a larger geometrical acceptance since no magnet is required. Al-
though detecting the cosmic-ray antinuclei as an indirect dark-matter signature is the primary goal
of GAPS, many low-energy cosmic-ray nuclei will also be recorded. Nuclei do not form exotic
atoms in the GAPS detectors, and their detection is based on the measurements of the ionization
energy depositions and the evaluation of the kinetic energy and the stopping depth relative to the
measured velocity. An algorithm was developed to fit the slow-down of particles and antiparticles
tracked inside the GAPS apparatus. The quantities fitted by this algorithm, together with the mea-
sured velocity and energy deposition information, allow the identification of protons, deuterons,
and helium nuclei and the measurement of their spectra in a low-energy range (< 0.25 GeV/n).
The results of this analysis, based on detailed Monte Carlo simulation studies, will be presented
in this contribution.