Stopping-Power Differences Between Positive and Negative Pions at Low Velocities

Measurements of grain densities of stopping ${\pi }^{+}$ and ${\pi }^{-}$ mesons in emulsion show that, in the velocity interval $0.051<\mathrm{}\beta <0.178\mathrm{}$, the energy-loss rates of ${\pi }^{+}$ mesons exceed that of the ${\pi }^{-}$ by amounts of 0 to 60 MeV/cm. The reported range differences between positive and negative particles are satisfactorily accounted for by the results of this experiment.