The average lifetime of b-baryons has been studied using 3 x 10(6) had
ronic Z(0) decays collected by the DELPHI detector at LEP. Three metho
ds have been used, based on the measurement of different observables:
the proper decay time distribution of 206 vertices reconstructed with
a Lambda, a lepton and an oppositely charged pion; the impact paramete
r distribution of 441 muons with high transverse momentum accompanied
by a Lambda in the same jet; and the proper decay time distribution of
125 Lambda(c)-lepton decay vertices with the Lambda(c) exclusively re
constructed through its pK pi, pK(0) and Lambda 3 pi decay modes. The
combined result is: [GRAPHICS] where the first systematic error is due
to experimental uncertainties and the second to the uncertainties in
the modelling of the b-baryon production and semi-leptonic decay, Incl
uding the measurement recently published by DELPHI based on a sample o
f proton-muon vertices, the average b-baryon lifetime is: [GRAPHICS] [
GRAPHICS]