Search for rare hadronic B decays

Abstract

A search for rare decays of B hadrons has been performed using approximately two million hadronic Z 0 decays collected by the OPAL experiment between 1990 and 1993. The exclusive decay channels B d 0 → π + π −, B d 0 → K +π −, B s 0 → π +K − and B s 0 → K +K − have been studied. Such decays include contributions from flavour changing neutral current processes such as hadronic penguin decays. No significant excess of events has been observed in the π +π −, π +K − and K +K − invariant mass distributions. Consequently, upper limits on the B d 0 branching ratios, Br(B d 0→ π + π −) < 4.7 × 10 −5 and Br(B d 0→K + π −) < 8.1 × 10 −5, and on the B s 0 branching ratios, Br(B s 0→ π +K −) < 2.6 × 10 −4 and Br(B s 0→K +K −) < 1.4 × 10 −4, have been set at the 90% confidence level. These limits assume that the ratio of the partial decay widths of the Z 0, λ (Z 0 → bb̄)/λ(Z 0 → hadrons), is 0.217 and that the fractions of B d 0 and B s 0 mesons produced during fragmentation are 39.5% and 12% respectively. The B s 0 branching ratio limits are the first such limits obtained.