Animated particle tracks showing the production and decay of sigma particles in the bubble chamber at Lawrence Berkeley Laboratory. Two negative kaons (blue) enter from left, and interact with protons in the chamber's liquid to produce characteristic short, kinked tracks of a positive sigma (red track, left) and a negative sigma (yellow track, right), along with negative and positive pions (green). The positive sigma decays to a positive pion (green) and a neutron (unseen as it is neutral). The negative sigma decays to a negative pion (green) and a neutron. Sigma particles are baryons comprising two up or down quarks and one strange, charm, bottom or top quark.