Abstract
We consider a warped five-dimensional model with an ultraviolet (UV) brane and, on top of the Standard Model isolated modes, continua of KK modes with different mass gaps for all particles: gauge bosons, fermions, graviton, radion and Higgs boson. The model can be considered as a modelization in five dimensions of gapped unparticles. The five dimensional metric has a singularity, at a finite (infinite) value of the proper (conformal) coordinate, which is admissible as it supports finite temperature in the form of a black hole horizon. An infrared (IR) brane, with particular jumping conditions, is introduced to trigger correct electroweak breaking. The gravitational metric is AdS5 near the UV brane, to solve the hierarchy problem with a fundamental Planck scale, and linear, in conformal coordinates, near the IR, as in the linear dilaton and five-dimensional clockwork models. The branes, and singularity, distances are fixed, à la Goldberger-Wise, by a bulk scalar field with brane potentials explicitly breaking the conformal symmetry. The bosonic continuum of KK modes with the smallest mass gap are those of gauge bosons, and so they are the most likely produced at the LHC. Mass gaps of the continuum of KK fermions do depend on their localization in the extra dimension. We have computed the spectral functions, and arbitrary Green’s functions, and shown how they can modify some Standard Model processes.
Highlights
Models [6], or better their five-dimensional (5D) continuum limit [7], the linear dilaton models [8], dual to Little String theories (LST) [9], which predict an continuum spectrum with a TeV mass gap and a mass separation between modes ∼ 30 GeV
This mechanism provides an alternative to the so-called custodial models where the bulk gauge symmetry is enlarged, to encompass custodial symmetry, to SU(2)L ⊗ SU(2)R ⊗ U(1)B−L, which is broken to SU(2)L ⊗ U(1)Y at the UV brane but conserved at the IR brane [20], or even custodial models where the symmetry in the bulk is an enlarged group G [21], and where the Higgs is identified with the fifth component of the 5D gauge field and where EW symmetry breaking proceeds dynamically
In this paper we will present the critical case of non-custodial models where the spectrum is continuum with a gap at the TeV scale, and the hierarchy problem is solved by a stabilizing scalar fielda la Goldberger-Wise [22]
Summary
We will assume the Higgs field to be propagating in the bulk and localized toward the IR brane in order to solve the hierarchy problem. Regarding the IR brane, a way to have matching conditions compatible with the EoM is by assuming λ1(v1) = λ1(v1) = 0, i.e. a brane potential of the form λ1(φ) γ1 Where c0 = ρz0 − γE − Γ(0, kys) −γE, with γE being the Euler’s constant In this case the domain of the conformal coordinate is z0 ≤ z < +∞. A(z) ρz − c0 − log(ρ/k) + O e−ρz , for z → +∞ In this way, both φ and A behave linearly in terms of the conformal coordinate in the IR region. A as functions of the conformal coordinate are shown in figure 1
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