Lambda(b) polarization in Z(0) decays at LEP

The longitudinal polarization of the Lambda(b) baryon is measured at the LEP e(+)e(-) collider by DELPHI. It is determined from the charged lepton and neutrino energy spectra in 249 +/- 19 Lambda(b) semileptonic decays reconstructed in approximate to 3.5 million hadronic Z(0) decays using Lambda(0)-lepton correlations. The measured polarization is: P- Lambda b = -0.49(-0.30)(+0.32)(stat.) +/- 0.17(syst.).