Oct 2017 - Sep 2018

Cosmic rays, anti-helium, and an old navy spotlight

by Kfir Blum

Thursday, 23 November 2017 from to (Europe/London)
at IPPP ( OC218 )
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 astrophysical flux? Astrophysical anti-nuclei are produced in pp collisions, where laboratory cross section data is scarce, so until very recently the relevant production cross section was essentially unknown. 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 prediction of coalescence. For anti-helium the resulting cross section is 1-2 orders of magnitude higher than earlier estimates. We show that very recent measurements by the ALICE experiment are consistent with the HBT prediction, and discuss some of the implications for both heavy ion physics and cosmic ray astrophysics. The astrophysical flux of anti-helium and anti-deuterium could be within reach of a five-year exposure of AMS02.