Measurement of the Čerenkov Radiation from Positive and Negative Pi Mesons

Čerenkov light pulses from individual ${\pi }^{+}$ and ${\pi }^{-}$ mesons from the Chicago cyclotron have been measured by using photomultipliers and Lucite radiators. An analysis of the pulse-height distributions has been made for comparing the velocity dependence of the radiation with the predictions of classical theory. Theory and experiment are in substantial agreement. However, saturation was found to set in at a somewhat lower energy than theory predicts for an end-window type tube (Dumont type 6363). A search was made for a difference in the photoeffect produced by positive and negative particles radiating Čerenkov light. The effect was found to be less than about 3 percent, the limit of resolution being determined by magnetic effects on photomultiplier gain.