Dimension-six CP-conserving operators of the third-family quarks and their effects on collider observables

We list all possible dimension-six CP-conserving SUc(3)× SUL(2)× UY (1) invariant operators involving the third-family quarks which could be generated by new physics at a higher scale. Expressions for these operators after electroweak gauge symmetry breaking and the induced effective couplings Wtb̄, Xbb̄ and Xtt̄ (X = Z, γ, g,H) are presented . Analytic expressions for the tree level contributions of all these operators to the observables Rb and A b FB at LEP I, σ(e e → bb̄) and AFB at LEP II, σ(ee → tt̄) and AFB at the NLC, as well as σ(pp̄ → tb̄+X) at the Tevatron upgrade, are provided. The effects of these operators on different electroweak observables are discussed and numerical examples presented. Numerical analyses show that in the coupling region allowed by Rb and AFB at LEP I, some of the new physics operators can still have significant contributions at LEP II, the Tevatron and the NLC.