A search for rare B meson decays at the CERN Spp̄S collider

Abstract We report on a search for the decays B 0 → μ + μ − , B → μ + μ − X and B d 0 → μ + μ − K 0∗ , which are expected to be rare if mediated by flavor changing neutral currents. Using data collected during the 1984–1989 CERN pp Collider runs, the UA1 search was carried out using μ + μ − events with 3.9 μμ c 2 . We find 90% confidence level upper limits on the branching for BR → μ + μ − of 8.3 × 10 −6 , for B → μ + μ − X of 5.0 × 10 −5 , and for B 0 d →μ + μ − K 0∗ of of 2.3 × 10 −5 . Implicatitions for upper limits on the t-quark mass are discussed.