Lifetimes of charged and neutral B hadrons using event topology

The lifetimes of charged and neutral B hadrons have been measured using data collected by the DELPHI experiment at LEP between 1991 and 1993. B hadrons are tagged as jets with a secondary vertex and the charge of the B candidate is taken to be the sum of the charges of the particles in the secondary vertex. Approximately 1,434,000 multihadronic \PZz decays yielded 1817 B hadron candidates. The B purity was estimated to be around 99.1\pm0.3\%, and 83\% (70\%) of the events measured as neutral (charged) came from neutral (charged) B's. The mean lifetimes of charged and neutral B hadrons were found to be \TAUBC\pm\ERRBC\;(stat.)\pm\SYSBC\;(syst.)~ps and \TAUBN\pm\ERRBN\;(stat.)\pm\SYSBN\;(syst.)~ps respectively. The ratio of their lifetimes, \tau_{charged}/\tau_{neutral}, was \RAT10^{\ERRCNP}_{\ERRCNM}\;(stat.)\pm\SYSR10\;(syst.). By making assumptions about the \PsB and \PlB states, the \PbBp and \PbBz meson lifetimes were determined to be \tau_{{\rm B}^+}=\TAUBP\pm\ERRBP\;(stat.)\pm\ SYSBP\;(syst.)~ps and \tau_{{\rm B}^0}=\TAUBZ\pm\ERRBZ\;(stat.)\pm \SYSBZ\;(syst.)~ps and the ratio of their lifetimes was:\\ \tau_{{\rm B}^+}/\tau_{{\rm B}^0} = \RATPZ^{\ERRPZP}_{\ERRPZM}\; \pm \SYSRP . The mean \PbB lifetime was also deduced to be <\tau_{{\rm B}}> = 1.64\pm0.06\; (\mbox{ stat.}) \pm\SYSB\;(\mbox{ syst.}) \; \mbox{ ps.}