Measurement of the AverageB- Hadron Lifetime

Results are reported from a study of the impact parameters of electrons in hadronic events produced at the PEP $e^{+}{e}^{-}$ storage ring. Electrons in hadronic events are produced by bottom and charm decay and their impact parameters show hadrons containing bottom quarks to have a lifetime of ${1.16}_{-0.34\mathrm{}}^{+0.37\mathrm{}}$(stat.) ±0.23 (syst.) psec. This result is used to constrain elements of the Kobayashi-Maskawa mixing matrix.