We compute the Coleman Weinberg effective potential for the Higgs field in RS Gauge-Higgs unification scenarios based on a bulk SO(5) × U (1) X gauge symmetry, with gauge and fermion fields propagating in the bulk and a custodial symmetry protecting the generation of large corrections to the T parameter and the coupling of the Z to the bottom quark. We demonstrate that electroweak symmetry breaking may be realized, with proper generation of the top and bottom quark masses for the same region of bulk mass parameters that lead to good agreement with precision electroweak data in the presence of a light Higgs. We compute the Higgs mass and demonstrate that for the range of parameters for which the Higgs boson has Standard Model-like properties, the Higgs mass is naturally in a range that varies between values close to the LEP experimental limit and about 160 GeV. This mass range may be probed at the Tevatron and at the LHC. We analyze the KK spectrum and briefly discuss the phenomenology of the light resonances arising in our model. High energy physics experiments in recent years have confirmed the predictions of the Standard Model (SM), a renormalizable, chiral gauge theory based on the group SUIn particular, the low energy dynamics of fermions and gauge bosons of the theory have been tested with great accuracy. The origin of masses of these fundamental particles, however, remains a mystery. In the SM, masses arise through the vacuum expectation value (vev) of a scalar field doublet, which spontaneously breaks the electroweak (EW) symmetryA physical, neutral scalar field, the so called Higgs field, appears in the spectrum. Information on the mass of this scalar particle may be obtained through the quantum corrections that it induces to the masses and couplings of the EW gauge bosons. Consistency of the SM predictions with experimental observations is improved for small values of the Higgs mass, m H , close to the current experimental bound, m H ≥ 114.4 GeV [1].There are several aspects of the mechanism of the origin of mass that demand explanation. On one hand, the scale of the spontaneous symmetry breaking is governed by the size of the scalar mass parameter appearing in the Higgs field effective potential, and is much smaller than the Planck scale, the only known mass scale in nature, besides the dynamical generated QCD scale Λ QCD . Moreover, this scale is associated with a negative value of the squared Higgs mass. There is, however, no dynamical explanation for the origin of the Higgs effective potential, or for the associated breakdown of the EW symmetry. Finally, the hierarchy of the fermion masses of the different generations remains unexplained.Warped extra dimensions provide a theoretically attractive framework for the solution of the hierarchy problem of the SM. For one extra spatial dimension as in RS1 [2], the curvature k in the extra dimension induces a warp factor on the four dimensional metric, which depends on the position in the extra dimension. The coordinate point, x 5 = 0, is associated with a t...

The recent LHC discovery of a Higgs-like resonance at 126 GeV suggests that the minimal supersymmetric standard model must be modified in order to preserve naturalness. A simple extension is to include a singlet superfield and consider the scale-invariant NMSSM, whose renormalizable superpotential contains no dimensionful parameters. This extension not only solves the µ-problem, but can easily accommodate a 126 GeV Higgs. We study the naturalness of the scale-invariant NMSSM taking into account the recent constraints from LHC searches, flavor physics and electroweak precision tests. We show that TeV-scale stop masses are still allowed in much of the parameter space with 5% tuning for a low messenger scale of 20 TeV, split families (with third-generation sleptons decoupled) and Higgs-singlet coupling λ of order one. For larger values of the Higgs-singlet coupling, which can relieve the tuning in the Higgs VEV, an additional tuning in the Higgs mass limits increasing the (lightest) stop mass beyond 1.2 TeV, the gluino mass above 3 TeV, and electroweak charginos and neutralinos beyond 400 GeV for a combined tuning better than 5%. This implies that the natural region of parameter space for the scale-invariant NMSSM will be fully explored at the 14 TeV LHC.

We compute the couplings of the zero modes and first excited states of gluons, W 's, Z gauge bosons, as well as the Higgs, to the zero modes and first excited states of the third generation quarks, in an RS Gauge-Higgs unification scenario based on a bulk SO(5) × U (1) X gauge symmetry, with gauge and fermion fields propagating in the bulk. Using the parameter space consistent with electroweak precision tests and radiative electroweak symmetry breaking, we study numerically the dependence of these couplings on the parameters of our model. Furthermore, after emphasizing the presence of light excited states of the top quark, which couple strongly to the Kaluza Klein gauge bosons, the associated collider phenomenology is analyzed. In particular, we concentrate on the possible detection of the first excited state of the top, t 1 , which tends to have a higher mass than the ones accessible via regular QCD production processes. We stress that the detection of these particles is still possible due to an increase in the pair production of t 1 induced by the first excited state of the gluon, G 1 .