While the nature of dark matter (DM) remains unknown, the search for anti-nuclei in space is a very promising channel for its discovery in the near future. Various models predict that low-energy antinuclei, such as anti-3He, stemming from DM are essentially free from the background originating from ordinary collisions between cosmic rays and interstellar medium. The inelastic interaction probability of anti-3He in the interstellar medium is an essential ingredient for calculations of the anti-3He flux near Earth.
The anti-3He inelastic interaction cross section was measured for the first time, using the ALICE detector material as an effective target. The results are described by the parameterisations used in Geant4 within two standard deviations. The measurement was used to estimate the transparency of our galaxy to the propagation of anti-3He, with the GALPROP code and a standard set of propagation parameters. It has been found that anti-3He nuclei can travel long distances of several kpc, with about 50% of nuclei produced in DM annihilation reaching the near-Earth environment. For the nuclei stemming from the cosmic-ray background the obtained transparency varies with increasing anti-3He momentum from 25% to 90%. The uncertainties associated with the anti-3He absorption are about 10-15%, representing a large improvement in the knowledge of the anti-3He inelastic interactions - previously it was not possible to quantify the uncertainty due to the lack of measurements.
ALICE Collaboration 2022 arXiv:2202.01549