Observations of π-B charge-flavor correlations and resonant Bπ and BK production

Abstract

Evidence is presented for kinematic and charge correlations of B mesons with charged pions and kaons. Using a new technique, a sample of over 80 000 partially reconstructed B mesons is obtained in 3.5·10⁶ hadronic Z⁰ decays recorded using the OPAL detector at LEP. The invariant mass distributions of B⁺π⁻ and B⁺K⁻ combinations show enhancements consistent with the decays of P-wave resonances of a b antiquark and a light quark. We observe an excess of 1738±195 B⁺π⁻ pairs with invariant masses in the range 5.60-5.85 GeV and an excess of 149±31 B⁺K⁻ pairs with invariant masses in the range 5.80–6.00 GeV. Labeling the observed enhancements generically as B^** we find

$$\begin{gathered} \frac{{BR(Z^0 \to \bar b \to B^{**0} \to B^{(*) + } \pi ^ - )}}{{BR(Z^0 \to \bar b \to B^ + )}} = 0.18 \pm 0.04, \hfill \\ \frac{{BR(Z^0 \to \bar b \to B_s^{**0} \to B^{(*) + } K^ - )}}{{BR(Z^0 \to \bar b \to B^ + )}} = 0.026 \pm 0.008, \hfill \\ \end{gathered} $$

where B^(*)+ indicates the sum of B⁺ and B^*+ and the errors include statistical and systematic contributions. From a study of π-B charge-flavor correlations we conclude that the production flavor of a B meson can be tagged with the charge of a pion in an appropriately chosen kinematic region, and that the performance of this flavor tag compares favorably in the$Z^0 \to q\bar q$ environment with lepton-based tags.