Limits on Flavor-Universal Colorons

A flavor-universal extension of the strong interactions was recently proposed in response to the apparent excess of high-$E_T$ jets in the inclusive jet spectrum measured at the Tevatron. The color octet of massive gauge bosons (`colorons') that is present in the low-energy spectrum of the model's Higgs phase is studied here. Experimental constraints already imply that the coloron mass must exceed 870-1000 GeV. The import of recent Tevatron data and the prospective input from future experiments are also mentioned

Z-->bb-bar in U(1)R symmetric supersymmetry.

We compute the one-loop corrections to the $Z \to b\bar{b}$ vertex in the $U(1)_R$ symmetric minimal supersymmetric extension of the standard model. We find that the predicted value of $R_b$ is consistent with experiment if the mass of the lighter top squark is no more than 180 GeV. Furthermore, other data combines to place a lower bound of 88 GeV on the mass of the light top squark. A top squark in this mass range should be accessible to searches by experiments at FNAL and LEP

Critical constraints on chiral hierarchies.

Critical dynamics constrains models of dynamical electroweak symmetry breaking in which the scale of high-energy physics is far above 1 TeV. A big hierarchy requires the high-energy theory to have a second-order chiral phase transition, near which the theory is described by a low-energy effective Lagrangian with composite Higgs scalars. As scalar theories with more than one 4 coupling can have a Coleman-Weinberg instability and a first-order transition, such dynamical EWSB models cannot always support a large hierarchy. If the large-Nc Nambu Jona-Lasinio model is a good approximation to the top-condensate and strong extended technicolor models, they will not produce acceptable EWSB. © 1993 The American Physical Society

Separating dijet resonances using the color discriminant variable

Color-singlet and color-octet vector bosons predicted in theories beyond the Standard Model have the potential to be discovered as dijet resonances at the LHC. A color-singlet resonance that has leptophobic couplings needs further investigation to be distinguished from a color-octet one. In previous work, we introduced a method for discriminating between the two kinds of resonances when their couplings are flavor-universal, using measurements of the dijet resonance mass, total decay width and production cross-section. Here, we describe two extensions of that work. First, we broaden the method to the case where the vector resonances have flavor non-universal couplings, by incorporating measurements of the heavy-flavor decays of the resonance. Second, we apply the method to separating vector bosons from color-octet scalars and excited quarks

The Top Triangle Moose

We introduce a deconstructed model that incorporates both Higgsless and top-color mechanisms. The model alleviates the typical tension in Higgsless models between obtaining the correct top quark mass and keeping delta-rho small. It does so by singling out the top quark mass generation as arising from a Yukawa coupling to an effective top-Higgs which develops a small vacuum expectation value, while electroweak symmetry breaking results largely from a Higgsless mechanism. As a result, the heavy partners of the SM fermions can be light enough to be seen at the LHC

Topcolor in the LHC Era

Ongoing LHC searches for the standard model Higgs Boson in WW or ZZ decay modes strongly constrain the top-Higgs state predicted in many models with new dynamics that preferentially affects top quarks. Such a state couples strongly to top-quarks, and is therefore produced through gluon fusion at a rate that can be greatly enhanced relative to the rate for the standard model Higgs boson. As we discuss in this talk, a top-Higgs state with mass less than 300 GeV is excluded at 95% CL if the associated top-pion has a mass of 150 GeV, and the constraint is even stronger if the mass of the top-pion state exceeds the top-quark mass or if the top-pion decay constant is a substantial fraction of the weak scale. These results have significant implications for theories with strong top dynamics, such as topcolor-assisted technicolor, top-seesaw models, and certain Higgsless models

Distinguishing flavor nonuniversal colorons from Z' bosons at the LHC

Electrically neutral massive color-singlet and color-octet vector bosons, which are often predicted in theories beyond the Standard Model, have the potential to be discovered as dijet resonances at the LHC. A color-singlet resonance that has leptophobic couplings needs further investigation to be distinguished from a color-octet one. In previous work, we introduced a method for discriminating between the two kinds of resonances when their couplings are flavor universal, using measurements of the dijet resonance mass, total decay width, and production cross section. Here, we describe an extension of that method to cover a more general scenario, in which the vector resonances could have flavor-nonuniversal couplings; essentially, we incorporate measurements of the heavy-flavor decays of the resonance into the method. We present our analysis in a model-independent manner for a dijet resonance with mass 2.5-6.0 TeV at the LHC with s=14TeV and integrated luminosities of 30, 100, 300, and 1000fb-1 and show that the measurements of the heavy-flavor decays should allow conclusive identification of the vector boson. Note that our method is generally applicable even for a Z' boson with non-Standard invisible decays. We include an Appendix of results for various resonance couplings and masses to illustrate how well each observable must be measured to distinguish colorons from Z's