Z→c bar c, b bar b decays and the aspon model

The aspon model predicts mixing of hypothetical new quarks with the standard model quarks. This mixing modifies the decay rates of the Z boson into quarks. In this paper, it is examined whether the measured values of Rb≡Γ(Z→b bar b)/Γ(Z→hadrons) and Rc≡Γ(Z→c bar c)/Γ(Z→hadrons) provide any constraints on the aspon model parameters. copyright 1998 The American Physical Society