When matter & antimatter meet?
The basic building block of material are gluons, quarks and leptons. Nucleons are baryons build from 3 quarks (up, up, down on proton; up, down, down on neutron) and 3 gluons holding them together. Antinucleons are build from 3 antiquarks and 3 gluos. When nucleon and antinucleon meet there is a chance that some of the quarks will miss so even in this case there will be leftovers… From these leftovers and possibly from energy of the collision new particles will form. Most of them are mesons build from 1 quark and 1 antiquark with gluon holding them together. It is even possible for this quark and antiquark to be pairs (for example up and anti-up), but in this case the meson is short lived and will decay faster than in the case where the antiquark is not the pair of quark. When oxygen is hit by anti-helium the most of the oxygen will miss totally the anti-helium and continue forward as free protons and neutrons. For those parts which collide with anti-helium the sequence of events is
