Measurement of the average polarization of b baryons in hadronic Z0 decays

G. Abbiendi, K. Ackerstaff, G. Alexander, J. Allison, N. Altekamp, K.J. Anderson, S. Anderson, S. Arcelli, S. Asai, S.F. Ashby, D. Axen, G. Azuelos (+308 others)
1998 Physics Letters B  
In the Standard Model, b quarks produced in e + e − annihilation at the Z 0 peak have a large average longitudinal polarization of −0.94. Some fraction of this polarization is expected to be transferred to b-flavored baryons during hadronization. The average longitudinal polarization of weakly decaying b baryons, P Λ b L , is measured in approximately 4.3 million hadronic Z 0 decays collected with the OPAL detector between 1990 and 1995 at LEP. Those b baryons that decay semileptonically and
more » ... duce a Λ baryon are identified through the correlation of the baryon number of the Λ and the electric charge of the lepton. In this semileptonic decay, the ratio of the neutrino energy to the lepton energy is a sensitive polarization observable. The neutrino energy is estimated using missing energy measurements. From a fit to the distribution of this ratio, the value is obtained, where the first error is statistical and the second systematic.
doi:10.1016/s0370-2693(98)01387-2 fatcat:wxvkhovjjna7nmgrppk6afajdu