  Antimatter nuclei in cosmic rays (CRs) are a promising tool for the indirect
detection of dark-matter annihilation signatures. However, the search of
new-physics signals in CRs relies on our knowledge of the astrophysical
antimatter background which, in turns, depends critically on the several
fragmentation cross-sections that regulate production and destruction of
antiparticles in the interstellar medium. In this work, we have re-evaluated
the astrophysical background of CR antiproton, antineutron, and antihelium
nuclei in Galactic CRs using improved calculations. The production
cross-sections of individual antinucleons are constrained using updated
calculations that make use of recent accelerator data. The production of
antideuteron and antihelium nuclei is calculated using an improved model of
nuclear coalescence that accounts for the asymmetry in antineutron and
antiproton production. We discuss the cross-section induced uncertainties and
show that they are dominating in comparison with other uncertainties of
astrophysical origin.
