Λ0b polarization at LEP

Theoretical predictions and experimental aspects of the Λ0b baryon polarization measurement at LEP are briefly presented. In the typical LEP process e+ e- → Z0 → f anti-f down-type quarks are born with a high (∼ -0.94) longitudinal polarization. In case of a heavy b quark its almost full transfer to the ground baryonic state Λ0b makes an important prediction of the HQET (Heavy Quark Effective Theory). At LEP the Λ0b polarization is experimentally accessible in its semileptonic decay mode through the lepton energy spectra. Moreover, since neutrino is predicted to be the decay product most sensitive to polarization its energy reconstructions is essential for the described method. First results on Λ0b polarization coming from the ALEPH collaboration is presented. (author). 9 refs