A precise measurement of the B+, B0 and mean b-hadron lifetime with the DELPHI detector at LEP I

Final results from the DELPHI Collaboration on the lifetime of B+ and B0 mesons and the mean b-hadron lifetime, are presented using the data collected at the Z0 peak in 1994 and 1995. Elaborate, inclusive, secondary vertexing methods have been employed to ensure a b-hadron reconstruction with good efficiency. To separate samples of B+ and B0 mesons, high performance neural network techniques are used that achieve very high purity signals. The results obtained are: $\tau_{{\mathrm B}^+}$ = 1.624 $\pm 0.014$ (stat) $\pm 0.018 $ (syst) ps $\tau_{{\mathrm B}^0}$ = 1.531 $\pm 0.021$ (stat) $\pm 0.031 $ (syst) ps $\frac{\tau_{{\mathrm B}^+}}{\tau_{{\mathrm B}^0}}$ = 1.060 $\pm 0.021$ (stat) $\pm 0.024$ (syst) and for the average b-hadron lifetime: $\tau_{{\mathrm b}}$ = 1.570 $\pm 0.005$ (stat) $\pm 0.008$ (syst) ps.