Search for the Bc meson in hadronic Z decays

Abstract A search for the B c meson decaying into the channels J ψπ + and J ψl + ν l (l = e or μ ) is performed in a sample of 3.9 million hadronic Z decays collected by the ALEPH detector. This search results in the observation of 0 and 2 candidates in each of these channels, respectively, while 0.44 and 0.81 background events are expected. The following 90% confidence level upper limits are derived: Br(Z→B c X Br(Z→q q Br(B c + → J ψπ + ) −5 , Br(Z→B c X Br(Z→q q Br(B c + → J ψl + vl ) −5 Another B c + → J ψ(e + e − )μ + ν μ candidate with very low background probability, found in an independent analysis, is also described in detail.