The standard model provides an excellent description of the observables measured at high energy lepton and hadron colliders. However, measurements of the forward-backward asymmetry of the bottom quark at CERN LEP suggest that the effective coupling of the right-handed bottom quark to the neutral weak gauge boson is significantly different from the value predicted by the standard model. Such a large discrepancy may be the result of a mixing of the bottom quark with heavy mirror fermions with masses of the order of the weak scale. To be consistent with the precision electroweak data, the minimal extension of the standard model requires the presence of vector-like pairs of $\mathrm{SU}\left(2\right)\mathrm{}$ doublet and singlet quarks. In this article, we show that such an extension of the standard model is consistent with the unification of gauge couplings and leads to a very rich phenomenology at the Fermilab Tevatron, the B factories and the CERN LHC. In particular, if the Higgs boson mass lies in the range $120\mathrm{GeV}\lesssim m_h\lesssim 180\mathrm{GeV},$ we show that run II of the Tevatron collider with $4–8{\mathrm{fb}}^{-1}$ of integrated luminosity will have the potential to discover the heavy quarks, while observing $3\sigma$ evidence of the Higgs boson in most of the parameter space.

• Received 14 August 2003

DOI:https://doi.org/10.1103/PhysRevD.69.053001