Animated particle tracks of the production and decay of a neutral xi particle. The xi zero is a baryon comprising an up quark and two strange quarks. Here, a negative kaon (pink) enters from left and interacts with a proton in the bubble chamber, creating a neutral xi and a neutral kaon (which leave no tracks), a negative pion (lower green track) and a positive pion (lower blue track). The xi heads rightwards unseen before decaying into a neutral lambda and a neutral pion, which also leave no tracks, but reveal themselves by their decays: the pion into the red and yellow tracks of an electron positron pair, and the lambda into a negative pion and a proton (green and purple). The upper green and blue tracks are pions from the original neutral kaon.