Prompt Jψ production in hadronic Z0 decays

Evidence is presented for the production of prompt Jψ mesons (not originating in b-hadron decays) in hadronic Z0 decays. Using a sample of 3.6 million hadronic events, 24 prompt Jψ candidates are identified from their decays into e+e and μ+μ pairs. The background is estimated to be 10.2 ± 2.0 events. The following branching ratio for prompt Jψ production is obtained: Br(Z0 → promptJψ + X) = (1.9 +- 0.7 ± 0.5 ± 0.5) · 10−4, where the first error is statistical, the second systematic and the third error accounts for uncertainties in the prompt Jψ production mechanism.

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