The Top Quark: Experimental Roots and Branches of Theory

The CDF and D0 experiments at the Fermilab Tevatron have discovered the top quark and provided first measurements of many of its properties. The small top sample gathered by Run I leaves open many possibilities for top physics beyond the standard model. Run II and the LHC (and eventually an LC) promise to deepen our knowledge of the top quark and its relationship to electroweak symmetry breaking.Comment: 14 pages, 9 figures; talk presented at HCP200

Top Theories

As the most recently discovered and heaviest quark, the top presents us with theoretical challenges. How are we to understand its properties within the larger effort to explain the origins of electroweak and flavor symmetry breaking ? This talk discusses some of the surprises the top quark may have in store for us and indicates how experiment may help us pinpoint the truth about top.Comment: 17 pages, 15 figures, Talk presented at Heavy Flavours 8, University of Southampton, England, July 25-29, 199

Efficient Allocations, Equilibria and Stability in Scarf's Economy

Scarf's economy has been a vehicle in understanding stability properties in exchange economies. The full set of market equilibria and Pareto optimal allocations for this economy has not been analysed. This paper aims to do that. Firstly, we examine the Pareto optima and we find three different classes. Only Class I exhausts the aggregate endowments of all the goods. Class II and III involve throwing away partially or totally one good in order to achieve Pareto efficiency. Secondly, we explore the price and endowment distribution combinations which sustain the different Pareto Optima as market equilibria. A Pareto optimum which involves throwing away the whole endowment of one of the goods is globally stable.Exchange economy, Complements, Stability

Correcting Market Failure Due to Interdependent Preferences: When Is Piecemeal Policy Possible?

Generally, implementation of Pigovian taxes to correct for market failure requires an enormous set of information. For each commodity-person combination a different tax is required to correct the resulting market inefficiency. In this paper, we analyse interdependent preferences and inefficiency of the market solution with the aim of finding conditions justifying simple rules for such taxes. We examine the utility possibility curve and Scitovsky community indifference curve, allowing for general utility interdependence and agent heterogeneity. In particular we show the equivalence of taxes derived from the Marshallian and compensated demand approaches. We move on to analyse the welfare cost of consumption externalities and show that it decomposes into part due to individuals choosing suboptimal quantities and part due to individuals using valuations that are not socially optimal. We show what forms of externality can justify simple policy corrections. In particular, we analyse the conditions which are required for the market failure to be corrected by: 1) specific indirect ad valorem taxes on commodities, 2) the same proportional tax rate on every commodity, 3) a proportional income tax rate on each individual. The conditions are related to the restrictions necessary to have H synthetic consumers without externalities who replicate behaviour of individuals with externalities. An example with two individuals and three goods concludes the paper.Consumption externalities; Piecemeal policy

Anomalous Gluon Self-Interactions and ttˉt \bar{t} Production

Strong-interaction physics that lies beyond the standard model may conveniently be described by an effective Lagrangian. The only genuinely gluonic CP-conserving term at dimension six is the three-gluon-field-strength operator $G^3$. This operator, which alters the 3-gluon and 4-gluon vertices form their standard model forms, turns out to be difficult to detect in final states containing light jets. Its effects on top quark pair production hold the greatest promise of visibility.Comment: Latex file using [aps,aipbook,floats,epsf]{revtex}. 12 pages, 4 Postscript figures. Full PS copy at http://smyrd.bu.edu/htfigs/htfigs.html Talk presented by EHS at the International Symposium on Vector Boson Self-Interactions, UCLA, Feb. 1-3, 199

Custodial Symmetry, Flavor Physics, and the Triviality Bound on the Higgs Mass

The triviality of the scalar sector of the standard one-doublet Higgs model implies that this model is only an effective low-energy theory valid below some cut-off scale Lambda. We show that the experimental constraint on the amount of custodial symmetry violation implies that the scale Lambda must be greater than of order 7.5 TeV. The underlying high-energy theory must also include flavor dynamics at a scale of order Lambda or greater in order to give rise to the different Yukawa couplings of the Higgs to ordinary fermions. This flavor dynamics will generically produce flavor-changing neutral currents. We show that the experimental constraints on the neutral D-meson mass difference imply that Lambda must be greater than of order 21 TeV. For theories defined about the infrared-stable Gaussian fixed-point, we estimate that this lower bound on Lambda yields an upper bound of approximately 460 GeV on the Higgs boson's mass, independent of the regulator chosen to define the theory. We also show that some regulator schemes, such as higher-derivative regulators, used to define the theory about a different fixed-point are particularly dangerous because an infinite number of custodial-isospin-violating operators become relevant.Comment: 15 pages, 7 ps/eps embedded figures, talk presented at the 1996 International Workshop on Perspectives of Strong Coupling Gauge Theories (SCGT 96), Nagoya, Japa

Colorons: Theory and Phenomenology

We briefly describe the structure and phenomenology of a flavor-universal extension of the strong interactions, focusing on the color-octet of massive gauge bosons (`colorons') present in the low-energy spectrum. We discuss current limits on the colorons and what future measurements may reveal