Higgs production and decay in models of a warped extra dimension with a bulk Higgs

Journal of High Energy Physics, Jan 2015

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 → γγ 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 →γγ 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.

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Higgs production and decay in models of a warped extra dimension with a bulk Higgs

Paul R. Archer 0 1 3 7 Marcela Carena 0 1 3 5 6 Adrian Carmona 0 1 2 3 Matthias Neubert 0 1 3 4 7 Open Access 0 1 3 c The Authors. 0 1 3 0 8093 Zu rich , Switzerland 1 Batavia , IL 60510 , U.S.A 2 Institut fu r Theoretische Physik, ETH Zu rich 3 Johannes Gutenberg University , 55099 Mainz , Germany 4 Department of Physics, LEPP, Cornell University 5 Theoretical Physics Department , Fermilab 6 Enrico Fermi Institute and KICP, University of Chicago 7 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)


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Paul R. Archer, Marcela Carena, Adrian Carmona. Higgs production and decay in models of a warped extra dimension with a bulk Higgs, Journal of High Energy Physics, 2015, pp. 60, Volume 2015, Issue 1, DOI: 10.1007/JHEP01(2015)060