Many types of physics beyond the standard model include an extended electroweak gauge group. If these extensions are associated with flavor symmetry breaking, the gauge interactions will not be flavor-universal. In this note we update the bounds placed by electroweak data on the existence of flavor non-universal extensions to the standard model in the context of topcolor assisted technicolor (TC2), noncommuting extended technicolor (NCETC), and the ununified standard model (UUM). In the first two cases the extended gauge interactions couple to the third generation fermions differently than to the light fermions, while in the ununified standard model the gauge interactions couple differently to quarks and leptons. The extra SU(2) triplet of gauge bosons in NCETC and UUM models must be heavier than about 3 TeV, while the extra Z boson in TC2 models must be heavier than about 1 TeV.

Using precision electroweak data, we put limits on noncommuting extended technicolor models. We conclude that these models are viable only if the ETC interactions are strong. Interestingly, these models predict a pattern of deviations from the standard model which can fit the data significantly better than the standard model does, even after taking into account the extra parameters involved. © 1996 The American Physical Society.

We explore corrections to electroweak parameters in the context of Extended Technicolor (ETC) models in which the ETC gauge-boson which generates the top-quark mass carries weak SU(2) charge. For mt≈150 GeV there exist potentially large corrections to the Z decay width to b-quarks. Interestingly, in contrast to the situation in ETC models where the gauge-boson which generates the top-quark mass is a weak SU(2) singlet, the corrections may increase the Z→bb branching ratio. © 1994.

Composite Higgs models based on the chiral symmetries of ``theory space'' can produce Higgs bosons with masses of order 100 GeV from underlying strong dynamics at scales up to 10 TeV without fine tuning. This talk argues that flavor-violating interactions generically arising from underlying flavor dynamics constrain the Higgs compositeness scale to be at least 75 GeV, implying that significant fine-tuning is required. Bounds from CP violation and weak isospin violation are also discussed.

A new heavy di-jet resonance could be discovered at the 14 TeV LHC. In this talk we present a strategy to reveal the nature of such a particle; in particular to discern whether it is a quark–antiquark [Formula: see text], quark–gluon [Formula: see text], or gluon–gluon [Formula: see text] resonance. The strategy is based on the study of the energy profiles of the two leading jets in the di-jet channel. Including statistical uncertainties in the signal and the QCD backgrounds, we show that one can distinguish between [Formula: see text], [Formula: see text], and [Formula: see text] resonances; an evaluation of systematic uncertainties in the measurement of the jet energy profile will require a detailed detector study once sufficient 14 TeV di-jet data is in hand.

The ununified standard model is an extension of the standard model that contains separate electroweak gauge groups for quarks and leptons. When it was originally proposed, data allowed the new gauge bosons to be quite light. We use recent data from precision electroweak measurements to put stringent bounds on the ununified standard model. In particular, at the 95% confidence level, we find that the ununified gauge bosons must have masses above about 2 TeV. © 1995.

We review the connection between mt and the Zbb̄ vertex in ETC models and demonstrate the power of the resulting experimental constraint on models with weak-singlet ETC bosons. Some efforts to bring ETC models into agreement with experimental data on the Zbb̄ vertex are mentioned, and the most promising one (non-commuting ETC) is discussed in detail.

We review the connection between $m_t$ and the $Zb\bar b$ vertex in ETC models and discuss the resulting experimental constraint on models with weak-singlet ETC bosons. We mention several recent efforts to bring ETC models into agreement with this constraint, and explore the most promising one (non-commuting ETC) in detail.

Extended technicolor theories generate potentially large corrections to the $\Zbb$ vertex. These can be observed in current experiments at LEP.