Abstract

Warped extra-dimension models in which the Higgs boson is allowed to propagate in the bulk of a compact AdS$_5$ space are conjectured to be dual to models featuring a partially composite Higgs boson. They offer a framework with which to investigate the implications of changing the scaling dimension of the Higgs operator, which can be used to reduce the constraints from electroweak precision data. In the context of such models, we calculate the cross section for Higgs production in gluon fusion and the $H\to\gamma\gamma$ decay rate and show that they are finite (at one-loop order) as a consequence of gauge invariance. The extended scalar sector comprising the Kaluza-Klein excitations of the Standard Model scalars is constructed in detail. The largest effects are due to virtual KK fermions, whose contributions to the cross section and decay rate introduce a quadratic sensitivity to the maximum allowed value $y_\ast$ of the random complex entries of the 5D anarchic Yukawa matrices. We find an enhancement of the gluon-fusion cross section and a reduction of the $H\to\gamma\gamma$ rate as well as of the tree-level Higgs couplings to fermions and electroweak gauge bosons. We perform a detailed study of the correlated signal strengths for different production mechanisms and decay channels as functions of $y_\ast$, the mass scale of Kaluza-Klein resonances and the scaling dimension of the composite Higgs operator.

Highlights

  • Ever increasing accuracy, thereby providing stringent constraints on models of electroweak symmetry breaking

  • The result obtained in [22] instead corresponds to the case of a narrow bulk Higgs, whose profile along the extra dimension can be resolved by high-mass KK states coupling to the Higgs boson

  • In this paper we have studied the modification of Higgs couplings and the associated collider phenomenology in a class of scenarios, in which the Higgs propagates in a warped extra dimension

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Summary

Electroweak symmetry breaking with a bulk Higgs

The primary focus of this work is to study Higgs physics in the context of RS-type scenarios, i.e. spaces in which the dimensionful parameters exist at the Planck scale, but an effective 4D electroweak scale is generated via gravitational red-shifting (warping). In the following we shall not consider the possibility that the bulk-Higgs scalar mixes with the radion field present in RS scenarios in which the distance between the two branes is stabilised dynamically by means of the Goldberger-Wise mechanism [27]. Irrespective of the values of these couplings, one finds that the effects of Higgs-radion mixing on the effective couplings of the physical Higgs boson to SM fermions and gauge bosons are suppressed by v2/Λ2TeV, where ΛTeV ∼ 10MKK denotes the warped-down UV cutoff of the theory. These effects are parametrically smaller than the corrections of order v2/MK2 K, which we compute in this work.

Extended scalar sector
Ghost sector
Fermion masses and Yukawa couplings
Higgs production and decay
Derivation of the Feynman rules
Higgs production via gluon fusion
Application to AdS5 space
Electroweak fit and determination of 5D parameters
Effective 4D Yukawa couplings and loss of perturbative control
Phenomenology
Numerical analysis
Higgs decays to fermions
Total Higgs decay width
LHC phenomenology
Discussion and conclusions
A Using completeness relations to evaluate the fermion loop
Findings
LMQ r1 b dra bMQ
Full Text
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