A systematic analysis of new physics effects in spin correlations in q qbar to t tbar

I show that there are eight new physics operators that contribute to top pair production and subsequent decay in interference with the leading SM process at the Tevatron and estimate their expected statistical inaccuracies. All fully differential cross sections are calculated in the {6-particle} phase space. The observation of angular correlations dramatically improves the accuracy of the extraction.Comment: 16 pages RevTeX, 2 embedded figure

Pairing in a three component Fermi gas

We consider pairing in a three-component gas of degenerate fermions. In particular, we solve the finite temperature mean-field theory of an interacting gas for a system where both interaction strengths and fermion masses can be unequal. At zero temperature we find a a possibility of a quantum phase transition between states associated with pairing between different pairs of fermions. On the other hand, finite temperature behavior of the three-component system reveals some qualitative differences from the two-component gas: for a range of parameters it is possible to have two different critical temperatures. The lower one corresponds to a transition between different pairing channels, while the higher one corresponds to the usual superfluid-normal transition. We discuss how these phase transitions could be observed in ultracold gases of fermionic atoms.Comment: 10 pages, 3 figure

Symmetry breaking via fermion 4-point functions

We construct the effective action and gap equations for nonperturbative fermion 4-point functions. Our results apply to situations in which fermion masses can be ignored, which is the case for theories of strong flavor interactions involving standard quarks and leptons above the electroweak scale. The structure of the gap equations is different from what a naive generalization of the 2-point case would suggest, and we find for example that gauge exchanges are insufficient to generate nonperturbative 4-point functions when the number of colors is large.Comment: 36 pages, uses Revtex and eps files for figure

New Axial Interactions at a TeV

We consider a heavy fourth family with masses lying in the symmetry breaking channel of a new strong gauge interaction. This interaction generates a heavy quark axial-type operator, whose effects can be enhanced through multiple insertions. In terms of the strength of this operator we can express new negative contributions to the S and T parameters and the shifts of the Z couplings to the third family. In particular we find that the new contribution to T is strongly constrained by the experimental constraints on the Z coupling to the tau.Comment: 14 pages, 1 figure, PRD versio