Cosmic-ray anti-deuterium and anti-helium have long been suggested as
probes of dark matter, as their secondary astrophysical production was
thought extremely scarce.
But how does one actually predict the secondary flux? Anti-nuclei are
dominantly produced in pp collisions, where laboratory cross section
data is lacking.
We make a new attempt at tackling this problem by appealing to a
scaling law of nuclear coalescence with the physical volume of the
hadronic emission region. The same volume is probed by Hanbury
Brown-Twiss (HBT) two-particle correlations.
We demonstrate the consistency of the scaling law with systems ranging
from central and off-axis AA collisions to pA collisions, spanning 3
orders of magnitude in coalescence yield. Extending the volume scaling
to the pp system, HBT data allows us to make a new estimate of
coalescence, that we test against preliminary ALICE pp data.
For anti-helium the resulting cross section is 1-2 orders of magnitude
higher than earlier estimates. The astrophysical secondary flux of
anti-helium could be within reach of a five-year exposure of AMS02.