In these pictures e^- and e⁺ beams, perpendicular to the screen, met and annihilated. The resulting quarks and antiquarks combined to produce mesons and baryons, whose tracks are shown.

On the left, three clusters, initiated by a quark, its antiquark, and a gluon, provide evidence for the existence of gluons. On the right, two back-to-back clusters of particles were initiated by a quark and its oppositely moving antiquark.