Inclusive J, ψ' and χ_c production in hadronic Z decays

Abstract

We report on measurements of the inclusive production of J, ψ' and χ_c mesons in hadronic Z decays, based on 3.2 million hadronic events collected using the L3 detector at LEP. The J and ψ mesons are reconstructed through their decays into lepton pairs, while the χ_c mesons are reconstructed via the decay mode χ_c→J + γ. The measured branching fractions are: Br(Z → J + X) = (3.40 ± 0.23 (stat.) ± 0.27 (sys.)) × 10^-3, Br(Z → ψ' + X) = (1.6 ± 0.5 (stat.) ± 0.3 (sys.)) × 10^-3, Br(Z →χ_c1 + X) = (2.7 ± 0.6 (stat.) ± 0.5 (sys.)) × 10^-3. In the absence of a clear χ_c2 signal, the upper limit at 90% C.L. is set: Br(Z →χ_c2 + X) < 3.2 × 10^-3.