Hadron radiation in leptonic Z decays

Abstract The rate for the final state radiation of hadrons in leptonic Z decays is evaluated, using as input experimental data for σ ( e + e − → hadrons) in the low energy region. Configurations with a lepton pair of large and a hardronic state of low invariant mass are dominant. A relative rate Λ l l had Λ l l = 6.3 × 10 −4 is calculated. This result is about twice prediction based on a parton model calculation with a quark mass of 300 MeV. The rate for secondary production of heavy quarks is calculated in the same formalism.