MPP Colloquium

The long journey of antinuclei in our Galaxy

by Prof. Laura Fabbietti (TUM)


Low-energy antinuclei in cosmic rays are considered a promising probe for indirect dark matter searches. Some dark matter candidates, such as the Weakly Interacting Massive Particles (WIMPs), are expected to annihilate in our galaxy and produce light antinuclei and other particles, which can be observed as cosmic rays at Earth. However, antinuclei can also be produced in ordinary cosmic ray collisions with interstellar gas particles. Thus, precise modelling of signal and background cosmic ray fluxes, including the inelastic losses in the interstellar medium, is required in order to draw conclusions from future measurements of cosmic ray antinuclei, for example by the AMS-02 or GAPS experiments. 

The ALICE Collaboration at the LHC recently made the first measurement of the momentum-dependent inelastic cross section of antihelium-3 nuclei on matter, employing the ALICE detector material as a target. The antihelium-3 inelastic cross sections have been obtained by applying the antimatter-to-matter ratio and TOF-to-TPC matching methods in pp and Pb-Pb collisions, respectively. The obtained inelastic cross sections have been implemented in the GALPROP propagation model to estimate the losses of antihelium-3 nuclei in the galaxy due to inelastic interactions with the interstellar medium. 

We will present the antihelium-3 cross-section measurement and the resulting transparency of our galaxy to the propagation of antihelium-3 from dark matter annihilation and ordinary cosmic-ray collisions. These results enable the first experimental uncertainties from inelastic losses on the antinuclei flux, and confirm that antihelium-3 nuclei are indeed a promising probe for new physics, such as indirect dark matter searches.