Fermions, scalars and Randall-Sundrum gravity on domain-wall branes
Rhys Davies, Damien P. George
备注：
16 pages, 3 figures; v2, added references and clarified discussion; v3, added figures with accompanying discussion; v4, modifications to spontaneous symmetry breaking discussion, version to appear in PRD
We analyse the general features of localisation of fermions and scalars in smoothed field-theoretical versions of the type 2 Randall- Sundrum braneworld model. A scalar field domain-wall forms the brane, inducing warped gravity, and we study the mass spectra of the matter fields in the dimensionally reduced theory. We demonstrate explicitly that both scalar and fermion fields exhibit a continuum of properly normalisable modes starting at zero mass. If discrete bound modes are present in the gravity-free case, these become resonances in the continuum, while off-resonant modes are highly suppressed on the brane. We describe briefly how another scalar field can be used to break a symmetry on the domain-wall while leaving it unbroken far from the wall, as has already been done in the flat space case. Finally we present numerical calculations for a toy model which demonstrates the decoupling of continuum modes at low energies, so the theory becomes four dimensional.
The extremely small branching ratio of $b\to ss{\bar d}$ decay in the Standard Model makes it a suitable channel to explore new-physics signals. We study this $ΔS=2$ process in Randall-Sundrum models, including the custodially protected and the bulk-Higgs Randall-Sundrum models. Exploring the experimentally favored parameter spaces of these models, it suggests a possible enhancement of the decay rate, compared to the Standard Model result, by at most two orders of magnitude.
The Randall Sundrum (RS) models receive significant constraints from the neutral Kaon system. The CP violating observable $ε_K$, in Randall Sundrum scenario, requires the lightest KK gluon to be heavier than $\sim$ 24 TeV. The constraint is even stronger in the Little Randall Sundrum models (LRS), $\gtrsim$ 32 TeV. The LRS models are motivated for their possible visibility at the Large Hardon Collider (LHC). We show that the stringent constraints from K-physics can be relaxed in the LRS models, in the presence of the Brane Localised Kinetic Terms (BLKT). In particular, for a range of values, a…
We investigate inflation with a class of concave inflaton potentials of the form $\sim ϕ^n$ $(0<n<1)$ in the Randall-Sundrum model with an infinite extra spatial dimension. We show that this class of models is much more in good agreement with observations compared to the standard inflation. We also find the range of the five-dimensional Planck scale ($M_5$) and show that large tensor-to-scalar ratios do not eliminate small-field inflation in braneworld cosmology.
Model building within the Randall-Sundrum (RS) framework generally involves placing the Standard Model fields in the bulk. Such fields may possess non-zero values for their associated brane-localized kinetic terms (BLKTs) in addition to possible bulk mass parameters. In this paper we clearly identify the regions of the RS model parameter space where the presence of bulk mass terms and BLKTs yield a setup which is free from both ghost and tachyon instabilities. Such physically acceptable parameter space regions can then be used to construct realistic and phenomenologically viable RS models.
Lepton flavor violation in the Randall-Sundrum model with bulk neutrinos
研究了含有体中微子的Randall-Sundrum模型中的轻子味破坏。格罗斯曼和诺伊伯特最近提出，微小中微子质量和大混合的存在可以用兰德尔-桑德拉姆背景中大量中微子的存在来解释。由于体中微子的零模波函数局域在Planck膜上，我们的膜上的Dirac Yukawa耦合被指数抑制到足以产生微小的中微子质量。然而，这些体中微子的卡鲁扎-克莱因模式的存在增强了轻子味违反过程，如$μ\to e γ$，从它们的质量下限可以推导出来。我们发现，第一KK模式必须比25 TeV更重，如果所有的中微子汤川耦合的顺序统一，这需要微调的希格斯质量参数。
We study the dijet production in Randall-Sundrum model at the LHC with QCD next-to-leading(NLO) order accuracy. Our results show that the QCD NLO corrections can increase the total cross sections by more than $80\%$ and reduce the scale dependence. We also explore in detail several important kinematic distributions at the NLO level. Moreover, we discuss the upper limits of the KK graviton excluded mass range and the allowed parameter space for the coupling constant and KK graviton mass, using the experiment data.
In Randall-Sundrum models, one typically expects the radion to be the lightest new "gravity" state, as it is dual to a composite pseudo-Goldstone boson associated with conformal symmetry breaking in the IR. Here, we investigate the effects of localized brane curvature on the properties of the radion in Goldberger-Wise stabilized Randall-Sundrum models. We point out that both the radion mass and coupling to brane matter are sensitive to the brane curvature. Radion/Higgs kinetic mixing, via an IR-localized non-minimal coupling to the Higgs, is also investigated, in relation to the ghost-like rad…
