Search for the Bc meson

Abstract In a sample of 3.02 million hadronic Z 0 decays collected by the DELPHI detector, 270 J ψ → l + l − candidates have been selected. A search for fully reconstructed B c ± mesons has yielded one B c ± → J ψ π ± candidate, no B c ± → J ψ l ± ν l candidates, and one B c ± → J ψ , π + π − π ± candidate, consistent with expected background in each channel. The following 90% confidence level upper limits are determined: Br(Z 0 → B c ± X) × Br(B c ± → J ψ π ± ) −4 and Br(Z 0 → B c ± X) × Br(B c ± → J ψ l ± ν l ) −5 , where the ranges quoted correspond to the range of predicted B c ± lifetimes from 0.4 to 1.4 ps, and Br(Z 0 → B c ± X) × Br(B c ± → J ψ π + π − π ± ) −4 , constant over the range of predicted B c ± lifetimes.