Nuclei of light antimatter atoms can travel undisturbed in our galaxy for long distances: this is the result of a study published on 12 December in the journal Nature Physics by the international collaboration of the ALICE experiment, and which saw a major contribution from INFN. By examining the interactions between the material composing the experimental apparatus of ALICE, one of the four large detectors at CERN’s LHC accelerator, and the antimatter produced in proton-heavy-ion collisions, researchers were able, for the first time, to determine the rate at which antihelium-3 nuclei are absorbed by ordinary matter. The measurement shows that there is little interaction between the light antimatter nuclei and ordinary matter, which makes up the Milky Way, providing important information for the search, conducted with space-based observatories or balloon probes, for those dark matter candidates that decaying could emit antihelium-3, antideuterium or antiproton nuclei, detectable in the vicinity of Earth. Through the use of the data obtained and a program capable of simulating the distribution of particles in galaxies, ALICE researchers were able to estimate the Milky Way’s transparencies with respect to antihelium-3 nuclei, i.e. the ability of our galaxy to let these antinuclei pass through without being absorbed. This was based on two different astrophysical models describing possible sources of antimatter, showing that in both cases antihelium-3 nuclei are able to travel long distances, several thousand light-years, undisturbed. In addition to providing valuable information for understanding the nature of space antimatter flows reaching the Earth’s vicinity, the measurement also provides evidence in favour of the validity of dark matter research conducted through the study of light antimatter nuclei.
