Determination of the lifetime of bottom hadrons

We have measured the mean lifetime of the hadrons containing b quarks that are produced in $e^{+}$ $e^{\mathrm{-}}$ annihilation at √s =29 GeV. We use the full sample of data collected by the MAC detector at the SLAC storage ring, PEP, including those recently acquired with a precision vertex detector. The result is ${\tau }_b$=[1.29±0.20(stat) ±0.07(syst) ps]×(1.00±0.15), where the last factor is the systematic uncertainty in the scale.