J/ψ and ψ′ production in hadronic Z0 decays

Abstract

The production of J/ψ mesons in Z0 decays is studied using 3.6 million hadronic events recorded by the OPAL detector at LEP. The inclusive Z0 to J/ψ and b-quark to J/ψ branching ratios are measured from the total yield of J/ψ mesons, identified from their decays into lepton pairs. The J/ψ momentum distribution is used to study the fragmentation of b-quarks. The production rate of ψ′ mesons, identified from their decays into a J/ψ and a π+π- pair, is measured as well. The following results are obtained: Br(Z0→J/ψ X) = (3.9 ± 0.2 ± 0.3) · 10-3 and Br(Z0→ψ′ X) = (1.6 ± 0.3 ± 0.2) · 10-3, where the first error is statistical and the second systematic. Finally the J/ψ sample is used to reconstruc..