First neutrino observation in a hydrogen bubble chamber. The world's first neutrino observation in a hydrogen bubble chamber was found November 13, 1970, on this historical photograph from the Zero Gradient Synchrotron's 12-foot bubble chamber at Argonne National Laboratory. The invisible neutrino strikes a proton where three particle tracks originate (right). The neutrino turns into a mu-meson, the long center track. The short track is the proton. The third track is a pi-meson created by the collision.
