BROOKHAVEN LABORATORY / SCIENCE PHOTO LIBRARY BROOKHAVEN LABORATORY / SCIENCE PHOTO LIBRARY
Bubble chamber photo of sigma particle decay. The sigma lives too briefly to be seen; its presence is deduced from other particles. A neutrino enters unseen at bottom & collides with a proton in the bubble chamber liquid, producing the sigma & a negative muon. The sigma decays to 1 negative & 3 positive pions, & a neutral lambda which leaves no track but betrays itself when it decays at lower centre (within the loop) to a proton & a negative pion. Negative particles curl anticlockwise, positive ones clockwise in the magnetic field. One positive pion is of lower energy & forms the loop; the muon & one of the pions knock out atomic electrons which produce the two spiral tracks.
Model release not required. Property release not required.