Density of Tracks of Protons and Mesons in Photographic Emulsions

THE experiments by von Friesen and Kristiansson described in the preceding communication indicate that, at the same velocity, π-mesons give a smaller track width than protons, and μ-mesons smaller than π-mesons. The pertinent velocities, c/5–c/3, lie below those of the Čerenkov effect.