Higgs production and decay in models of a warped extra dimension with a bulk Higgs
Paul R. Archer
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Marcela Carena
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Adrian Carmona
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Matthias Neubert
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Open Access
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c The Authors.
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8093 Zu rich
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Switzerland
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Batavia
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IL 60510
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U.S.A
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Institut fu r Theoretische Physik, ETH Zu rich
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Johannes Gutenberg University
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55099 Mainz
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Germany
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Department of Physics, LEPP, Cornell University
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Theoretical Physics Department
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Fermilab
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Enrico Fermi Institute and KICP, University of Chicago
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PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics
Warped extra-dimension models in which the Higgs boson is allowed to propagate in the bulk of a compact AdS5 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 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 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 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, the mass scale of Kaluza-Klein resonances and the scaling dimension of the composite Higgs operator.
1 Introduction 2 Electroweak symmetry breaking with a bulk Higgs 3
Higgs production and decay
Higgs mechanism in a generic 5D space
Extended scalar sector
Fermion masses and Yukawa couplings
Derivation of the Feynman rules
H W W and H ZZ decay rates
Higgs production via gluon fusion
Application to AdS5 space
Scalar profiles, vector profiles, and Higgs VEV
Electroweak fit and determination of 5D parameters
Effective 4D Yukawa couplings and loss of perturbative control
Numerical analysis
H W W and H ZZ decays
Higgs decays to fermions
Total Higgs decay width
LHC phenomenology
Discussion and conclusions
A Using completeness relations to evaluate the fermion loop
Introduction
The discovery of the Higgs boson marks the beginning of a new era in particle physics. It
represents the completion of the standard model (SM), but it also means the gauge
hierarchy problem ceases to be merely a theoretical puzzle. The measurements of the Higgs
couplings introduce a new set of constraints on beyond-the-standard-model (BSM)
scenarios, which complement those coming from electroweak precision tests and flavour physics.
The LHC, as well as other possible future colliders, will measure the Higgs couplings with
ever increasing accuracy, thereby providing stringent constraints on models of electroweak
symmetry breaking. Hence, if we are to have any hope of experimentally distinguishing
between the multitude of BSM scenarios, it is important to have a clear understanding of
how respective models modify the Higgs couplings.
This paper seeks to investigate how such Higgs couplings are modified in a class of
models in which the Higgs propagates in a fifth dimension, with particular emphasis on
a slice of five-dimensional (5D) anti-de Sitter space (AdS5). There has been considerable
interest in the phenomenological implications of such a space following the proposal of
the Randall-Sundrum (RS) model [1] as a non-supersymmetric resolution to the gauge
hierarchy problem, as well as the associated description of flavour hierarchies [24]. In the
most frequently studied version of the RS model, the Higgs is strictly localised to one of
the branes on the boundary of the space. However, there is no compelling reason why the
Higgs should have a special status as the only brane-localised particle, since a partially
delocalized Higgs can also provide a resolution to the hierarchy problem. In addition,
allowing the Higgs to propagate in the bulk helps alleviating some of the tensions with
electroweak precision tests [57] and flavour physics [810], it also offers some explanation
of the small scale of neutrino masses [1113] and is consistent with extensions that include
a dark matter candidate [1416].
When considering the implications for Higgs physics, there are a couple of more
fundamental motivations for considering a bulk Higgs. Firstly, under the AdS/CFT
correspondence a bulk Higgs is conjectured to be dual to an elementary Higgs mixing with the bound
states of a broken conformal field theory, i.e. a partially composite Higgs. By varying the
5D Higgs (...truncated)