Moderation and Absorption Times of Negative Pions in Liquid Hydrogen

Among 546 000 negative pions stopping in a liquid hydrogen bubble chamber, 21 events were found corresponding to pion-muon decay in the backward hemisphere from a $\mathrm{velocity}<~0.006c$. Analysis gives (2.3±0.6)×${10}^{-12\mathrm{}}$ sec as the mean time for a pion to go from this velocity to nuclear capture. Results are also presented for the moderation time of pions between velocities $0.1c$ and $0.006c$.