A precise measurement of the B+, B-0 and mean b-hadron lifetime with the DELPHI detector at LEP I

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