MEASUREMENT OF LAMBDA-B PRODUCTION AND LIFETIME IN Z0 HADRONIC DECAYS

Evidence for the production of b-flavoured baryons in Z0 decays is reported from the analysis of 365 000 hadronic events collected by the DELPHI detector. Assuming that most of the weakly decaying b flavoured baryons produced by the Z0 are LAMBDA(b), the observed signal of (LAMBDAl- + LAMBDAl+BAR) pairs, where l is a high transverse momentum lepton in the same jet as the LAMBDA, leads to a production rate: f (b --> LAMBDA(b)) x Br(LAMBDA(b) --> LAMBDAlnuX) = (0.41 +/- 0.13 +/- 0.09)%. Using a sample of 18 reconstructed LAMBDA(b) decay vertices, the lifetime is determined to be tau(LAMBDA(b)) = ( 1.04(-0.38)+0.48 +/- 0.10) ps.