Hydrogen-antihydrogen collisions

Matter-antimatter interactions are investigated using hydrogen-antihydrogen collisions as an example. Cross sections for elastic scattering and for th e antihydrogen loss (either through the rearrangement reaction, resulting i n formation of protonium and positronium according to H + (H) over bar --> p (p) over bar + e(+)e(-), or via annihilation in flight) are calculated fo r the first time in a fully quantum mechanical approach. Implications for e xperiments intending to trap and cool antihydrogen are discussed.