Phenomenology of a top quark seesaw model - art. no. 055002

The top quark seesaw mechanism offers a method for constructing a composite Higgs field without the usual difficulties that accompany traditional tech nicolor or top-color theories. The focus of this article is to study the ph enomenology of the new physics required by this mechanism. After establishi ng a set of criteria for a plausible top quark seesaw theory, we develop tw o models, the first of which has a heavy weak singlet fermion with hypercha rge 4/3 while the second has, in addition, a heavy weak singlet hypercharge - 2/3 fermion. At low energies, these theories contain one or two Higgs do ublets, respectively. We then derive the low energy effective Higgs potenti al in detail for the two-doublet theory as well as study the likely experim ental signatures for both theories. A strong constraint on the one-doublet model is the measured value of the rho parameter which permits the new heav y fermion to have a mass of about 5-7 TeV, when the Higgs boson has a mass greater than 300 Gev. In the two-doublet model mixing of the new heavy Y = - 2/3 fermion and the quark affects the prediction for R-b. In order to agr ee with the current limits on R-b, the mas of this fermion should be at lea st 12 TeV. The mass of the heavy Y = 4/3 fermion in the two-doublet model i s not as sharply constrained by experiments and can be as light as 2.5 TeV.