The fermion mass hierarchy in models with warped extra dimensions and a bulk Higgs

108

A comprehensive, five-dimensional calculation of Higgs-boson production in gluon fusion is performed for both the minimal and the custodially protected RandallSundrum (RS) model, with Standard Model fields propagating in the bulk and the scalar sector confined on or near the IR brane. For the first time, an exact expression for the gg → h amplitude in terms of the five-dimensional fermion propagator is derived, which includes the full dependence on the Higgs-boson mass. Various results in the literature are reconciled and shown to correspond to different incarnations of the RS model, in which the Higgs field is either localized on the IR brane or is described in terms of a narrow bulk state. The results in the two scenarios differ in a qualitative way: the gg → h amplitude is suppressed in models where the scalar sector is localized on the IR brane, while it tends to be enhanced in bulk Higgs models. In both cases, effects of higher-dimensional operators contributing to the gg → h amplitude at tree level are shown to be numerically suppressed under reasonable assumptions. There is no smooth cross-over between the two scenarios, since the effective field-theory description breaks down in the transition region. A detailed phenomenological analysis of Higgs production in various RS scenarios is presented, and for each scenario the regions of parameter space already excluded by LHC data are derived.

“…Our discussion will follow the expositions given in [38,57], but we will generalize these results in some aspects.…”

Section: B Case Of a Bulk-higgs Fieldmentioning

confidence: 87%

Section: Jhep01(2014)173mentioning

confidence: 99%

5D perspective on Higgs production at the boundary of a warped extra dimension

Malm

Neubert

Novotny

et al. 2014

108

“…It is well known that models with a brane-localized Higgs and no custodial symmetry suffer from large constraints imposed by electroweak precision tests [37,38]. However, the tensions with electroweak precision tests [39][40][41][42] and flavour physics [42][43][44][45] can be significantly reduced in the case of a 5D Higgs field living in the bulk, offering a new elegant explanation for the the tiny neutrino masses [46,47]. That is to say, a SU(2) L doublet bulk Higgs field…”

Section: Basic Structure Of the Modelmentioning

confidence: 99%

Warped flavor symmetry predictions for neutrino physics

Chen

Ding

Rojas

et al. 2016

A realistic five-dimensional warped scenario with all standard model fields propagating in the bulk is proposed. Mass hierarchies would in principle be accounted for by judicious choices of the bulk mass parameters, while fermion mixing angles are restricted by a ∆(27) flavor symmetry broken on the branes by flavon fields.The latter gives stringent predictions for the neutrino mixing parameters, and the Dirac CP violation phase, all described in terms of only two independent parameters at leading order. The scheme also gives an adequate CKM fit and should be testable within upcoming oscillation experiments.

“…This has been done in detail in ref. [44]. The author finds that, although one can go to unitary gauge with out any problems, there are physical pseudo-scalars in the spectrum which could provide a test for these models at the LHC.…”

Section: Jhep06(2015)066mentioning

confidence: 99%

Non-custodial warped extra dimensions at the LHC?

Huber

2015

With the prospect of improved Higgs measurements at the LHC and at proposed future colliders such as ILC, CLIC and TLEP we study the non-custodial RandallSundrum model with bulk SM fields and compare brane and bulk Higgs scenarios. The latter bear resemblance to the well studied type III two-Higgs-doublet models. We compute the electroweak precision observables and argue that incalculable contributions to these, in the form of higher dimensional operators, could have an impact on the T -parameter. This could potentially reduce the bound on the lowest Kaluza-Klein gauge boson masses to the 5 TeV range, making them detectable at the LHC. In a second part, we compute the misalignment between fermion masses and Yukawa couplings caused by vector-like KaluzaKlein fermions in this setup. The misalignment of the top Yukawa can easily reach 10%, making it observable at the high-luminosity LHC. Corrections to the bottom and tau Yukawa couplings can be at the percent level and detectable at ILC, CLIC or TLEP.