Revealed: Positronium's behavior in particle billiards

Collision physics can be like a game of billiards. Yet in the microscopic world, the outcome of the game is hard to predict. Fire a particle at a group of other particles, and they may scatter, combine or break apart, according to probability distributions governed by quantum mechanics. These processes can tell us about fundamental properties of matter and, if antimatter projectiles are used, also about matter-antimatter interactions.