12 research outputs found
Impact of Warped Extra Dimensions on the Dipole Coefficients in Transitions
We calculate the electro- and chromomagnetic dipole coefficients
and in the context of the minimal
Randall-Sundrum (RS) model with a Higgs sector localized on the IR brane using
the five-dimensional (5D) approach, where the coefficients are expressed in
terms of integrals over 5D propagators. Since we keep the full dependence on
the Yukawa matrices, the integral expressions are formally valid to all orders
in . In addition we relate our results to the expressions
obtained in the Kaluza-Klein (KK) decomposed theory and show the consistency in
both pictures analytically and numerically, which presents a non-trivial
cross-check. In Feynman-'t Hooft gauge, the dominant corrections from virtual
KK modes arise from the scalar parts of the -boson penguin diagrams,
including the contributions from the scalar component of the 5D gauge-boson
field and from the charged Goldstone bosons in the Higgs sector. The size of
the KK corrections depends on the parameter , which sets the upper
bound for the anarchic 5D Yukawa matrices. We find that for
the dominant KK corrections are proportional to . We discuss the
phenomenological implications of our results for the branching ratio , the time-dependent CP asymmetry , the
direct CP asymmetry and the CP asymmetry difference
. We can derive a lower bound on the first KK
gluon resonance of TeV for , requiring that at least of
the RS parameter space covers the experimental error margins. We
further discuss the branching ratio and compare
our predictions for and with
phenomenological results derived from model-independent analyses.Comment: 44 pages plus appendix, 10 figures, added equations (58) and (61
Higgs Couplings and Phenomenology in a Warped Extra Dimension
We present a comprehensive description of the Higgs-boson couplings to
Standard Model fermions and bosons in Randall-Sundrum (RS) models with a Higgs
sector localized on or near the infra-red brane. The analytic results for all
relevant Higgs couplings including the loop-induced couplings to gluons and
photons are summarized for both the minimal and the custodial RS model. The RS
predictions for all relevant Higgs decays are compared with current LHC data,
which already exclude significant portions of the parameter space. We show that
the latest measurements are sensitive to KK gluon masses up to at confidence level for anarchic 5D Yukawa couplings
bounded from above by . We also derive the sensitivity
levels attainable in the high-luminosity run of the LHC and at a future linear
collider.Comment: 28 pages plus appendix, 9 figures; equation (52) corrected,
references update
5D Perspective on Higgs Production at the Boundary of a Warped Extra Dimension
A comprehensive, five-dimensional calculation of Higgs-boson production in
gluon fusion is performed for both the minimal and the custodially protected
Randall-Sundrum (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.Comment: 44 pages (plus appendices), 6 figures; several improvements of the
discussion, new section estimating the effects of brane-localized
higher-dimensional operator
Higgs Decay into Two Photons at the Boundary of a Warped Extra Dimension
A detailed five-dimensional calculation of the Higgs-boson decay into two
photons is performed in both the minimal and the custodially protected
Randall-Sundrum (RS) model, where the Standard Model (SM) fields propagate in
the bulk and the scalar sector lives on or near the IR brane. It is explicitly
shown that the gauge invariance of the sum of diagrams involving
bosonic fields in the SM also applies to the case of these RS scenarios. An
exact expression for the amplitude in terms of the
five-dimensional (5D) gauge-boson and fermion propagators is presented, which
includes the full dependence on the Higgs-boson mass. Closed expressions for
the 5D -boson propagators in the minimal and the custodial RS model are
derived, which are valid to all orders in . In contrast to
the fermion case, the result for the bosonic contributions to the
amplitude is insensitive to the details of the localization
of the Higgs profile on or near the IR brane. The various RS predictions for
the rate of the process are compared with the latest
LHC data, and exclusion regions for the RS model parameters are derived.Comment: 30 pages (plus appendices), 4 figures (V2: several improvements of
the discussion, discussion of the lepton sector added, typos corrected,
references added
Five-dimensional perspective on Higgs physics and the b to s gamma transition in a warped extra dimension
This thesis studies the Higgs-boson production and decay processes as well as the flavor-changing neutral current b to s gamma in models with one warped extra dimension, where the gauge bosons and fermions propagate into the bulk and the Higgs sector is localized on or near the infra-red brane. These so-called Randall-Sundrum models present attractive scenarios beyond the Standard Model of particle physics that can address the disparity between the electroweak and the Planck scale. Furthermore, these models provide a natural explanation for the hierarchical pattern observed in the flavor sector and the smallness of flavor-changing neutral currents.Die vorliegende Arbeit befasst sich mit den Produktions- und Zerfallsprozessen des Higgs-Bosons sowie dem Flavor-ändernden neutralen Strom b nach s gamma in Modellen mit einer gekrümmten Extradimension, in denen die Eichbosonen und Fermionen im Bulk propagieren, während der Higgs-Sektor auf oder nahe der infraroten Brane lokalisiert ist. Diese sogenannten Randall-Sundrum Modelle stellen vielversprechende Szenarien dar, die über die Physik des Standardmodells hinausgehen und den Größenunterschied zwischen der elektroschwachen und der Planck Skala erklären können. Weiterhin bieten diese Modelle eine natürliche Erklärung für das hierarchische Muster im Flavor-Sektor und für die Unterdrückung von Flavor-ändernden neutralen Strömen
A Solution to the Flavor Problem of Warped Extra-Dimension Models
A minimal solution to the flavor problem of warped extra-dimension models,
i.e. the excessive mixed-chirality contribution to CP violation in K-Kbar
mixing arising from Kaluza-Klein (KK) gluon exchange, is proposed. Extending
the strong-interaction gauge group in the bulk by an additional SU(3), and
breaking this symmetry to QCD via boundary conditions, the constraints arising
from the epsilon_K parameter are significantly relaxed. As a result, KK scales
M_KK ~ 2 TeV are consistent with all flavor observables without significant
fine-tuning. The model predicts the existence of an extended Higgs sector
featuring massive color-octet scalars and a tower of KK pseudo-axial gluon
resonances, whose existence is not in conflict with recent LHC dijet bounds.Comment: Added discussion of the extended scalar sector and its impact on the
choice of boundary conditions. Corrected the Wilson coeffcients in (12) by a
symmetry factor of 1/2 and updated the plots in Figure 2 with improved
fitting functions. Main conclusions unchange