B production in Z decays.

The decay B→ B has been observed with the DELPHI detector at LEP, where the B meson is produced in Z boson decays. The combination of inclusively reconstructed B mesons with well-measured converted photons yields a measurement of the flavour-averaged B- B mass difference of 45.5±0.3 (stat.) ±0.8 (syst.) MeV/c. 95% confidence level upper limits at 6 MeV/c are placed on both the isospin (i.e. B- B) and the B- B splitting of the mass difference. The production ratio of B to B mesons in Z decays is measured to be 0.72±0.03 (stat.) ±0.06 (syst.). Limits on the production cross-section of other hypothetical excited B hadron states decaying radiatively are established. The differential B cross section has been measured to be in good agreement with the average b fragmentation, yielding an average fractional B energy of 〈 x〉=0.695±0.009 (stat.) ±0.013 (syst.). From the decay angular distribution the relative contribution of longitudinal B polarisation states is measured to be σ/(σ + σ) = 0.32 ± 0.04 (stat.) ±0.03 (syst.). [ABSTRACT FROM AUTHOR]