The contribution to precision electroweak measurements due to TeV physics which couples primarily to the W* and Z bosons may be parametrized in terms of the three "oblique correction" parameters, S, T, and U. We extend this parametrization to physics at much lower energies, 2 100 GeV, and show that in this more general case neutral-current experiments are sensitive to only two additional parameters. A third new parameter enters into the W* width.PACS number(s): 12.15.Lk, 12.60. -i

Using effective-Lagrangian techniques we perform a systematic survey of the lowest-dimension effective interactions through which heavy physics might manifest itself in present experiments. We do not restrict ourselves to special classes of effective interactions (such as "oblique" corrections). We compute the effects of these operators on all currently well-measured electroweak observables, both at low energies and at the Z resonance, and perform a global fit to their coefficients. Despite the fact that a great many operators arise in our survey, we find that most are quite strongly bounded by the current data. We use our-survey to systematically identify those effective interactions which are not well bounded by the data-these could very well include large new-physics contributions. Our results may also be used to efficiently confront specific models for new physics with the data, as we illustrate with an example.PACS number(s): 12.60. -i

We consider supersymmetry breaking communicated entirely by the superconformal anomaly in supergravity. This scenario is naturally realized if supersymmetry is broken in a hidden sector whose couplings to the observable sector are suppressed by more than powers of the Planck scale, as occurs if supersymmetry is broken in a parallel universe living in extra dimensions. This scenario is extremely predictive: soft supersymmetry breaking couplings are completely determined by anomalous dimensions in the effective theory at the weak scale. Gaugino and scalar masses are naturally of the same order, and flavor-changing neutral currents are automatically suppressed. The most glaring problem with this scenario is that slepton masses are negative in the minimal supersymmetric standard model. We point out that this problem can be simply solved by coupling extra Higgs doublets to the leptons. Lepton flavor-changing neutral currents can be naturally avoided by approximate symmetries. We also describe more speculative solutions involving compositeness near the weak scale. We then turn to electroweak symmetry breaking. Adding an explicit µ term gives a value for Bµ that is too large by a factor of ∼ 100. We construct a realistic model in which the µ term arises from the vacuum expectation value of a singlet field, so all weak-scale masses are directly related to m 3/2 . We show that fully realistic electroweak symmetry breaking can occur in this model with moderate fine-tuning. *

The ST U formalism of Peskin and Takeuchi is an elegant method for encoding the measurable effects of new physics which couples to light fermions dominantly through its effects on electroweak boson propagation. However, this formalism cannot handle the case where the scale of new physics is not much larger than the weak scale. In this case three new parameters (V, W and X) are required. We perform a global fit to precision electroweak data for these six parameters. Our results differ from what is found for just ST U . In particular we find that the preference for S < 0 is not maintained.

Recently, a scenario has been proposed in which the gravitational scale could be as low as the TeV scale, and extra dimensions could be large and detectable at the electroweak scale. Although supersymmetry is not a requirement of this scenario, it is nevertheless true that its best-motivated realizations arise in supersymmetric theories ͑such as M theory͒. We argue here that supersymmetry can have robust, and in some instances fatal, implications for the expected experimental signature for TeV-scale gravity. The signature of the supersymmetric version of the scenario differs most dramatically from what has been considered in the literature because mass splittings within the gravity supermultiplet in these models are extremely small, implying in particular the existence of a very light spin-one superpartner for the graviton. We compute the implications of this graviphoton, and show that it can acquire dimension-four couplings to ordinary matter which can strongly conflict with supernova bounds.