This is an actual bubble chamber photograph of an antiproton (entering from the bottom of the picture), colliding with a proton (at rest), and annihilating. Eight pions were produced in this annihilation. One decayed into a ⁺ and a . The paths of positive and negative pions curve opposite ways in the magnetic field, and the neutral  leaves no track.

Bubble chambers are an older type of detector. As charged particles pass through a bubble chamber, they leave a trail of tiny bubbles that make it easy to track the particles.

We have talked a lot about decays and annihilations, so let's now look at some examples of these processes.