Radiative electroweak symmetry breaking in a Little Higgs model

We present a new Little Higgs model, motivated by the deconstruction of a five-dimensional gauge-Higgs model. The approximate global symmetry is SO(5)(0)xSO(5)(1), breaking to SO(5), with a gauged subgroup of [SU(2)(0L) x U(1)(0R)] x O(4)(1), breaking to SU(2)(L) xU(1)(Y). Radiative corrections produce an additional small vacuum misalignment, breaking the electroweak symmetry down to U(1)(EM). Novel features of this model are: the only un-eaten pseudo-Goldstone boson in the effective theory is the Higgs boson; the model contains a custodial symmetry, which ensures that (T) over cap = 0 at tree-level; and the potential for the Higgs boson is generated entirely through one-loop radiative corrections. A small negative mass-squared in the Higgs potential is obtained by a cancellation between the contribution of two heavy partners of the top quark, which is readily achieved over much of the parameter space. We can then obtain both a vacuum expectation value of v = 246 GeV and a light Higgs boson mass, which is strongly correlated with the masses of the two heavy top quark partners. For a scale of the global symmetry breaking of f = 1 TeV and using a single cutoff for the fermion loops, the Higgs boson mass satisfies 120 GeV less than or similar to MH less than or similar to 150 GeV over much of the range of parameter space. For f raised to 10 TeV, these values increase by about 40 GeV. Effects at the ultraviolet cutoff scale may also raise the predicted values of the Higgs boson mass, but the model still favors MH less than or similar to 200 GeV.