hep-ph/0204109
Constraints on the SU(3) Electroweak Model
Authors: Csaba Csaki, Joshua Erlich, Graham D. Kribs, John Terning
We consider a recent proposal by Dimopoulos and Kaplan to embed the
electroweak SU(2)_L X U(1)_Y into a larger group SU(3)_W X SU(2) X U(1)
at a scale above a TeV. This idea is motivated by the prediction for the
weak mixing angle sin^2 theta_W = 1/4, which naturally appears in these
models so long as the gauge couplings of the high energy SU(2) and U(1)
groups are moderately large. The extended gauge dynamics results in new
effective operators that contribute to four-fermion interactions and Z pole
observables. We calculate the corrections to these electroweak precision
observables and carry out a global fit of the new physics to the data. For
SU(2) and U(1) gauge couplings larger than 1, we find that the 95% C.L. lower
bound on the matching (heavy gauge boson mass) scale is 11 TeV. We comment on
the fine-tuning of the high energy gauge couplings needed to allow matching
scales above our bounds. The remnants of SU(3)_W breaking include multi-TeV
SU(2)_L doublets with electric charge (+-2,+-1). The lightest charged gauge
boson is stable, leading to cosmological difficulties.