Higgs Pair Production at the LHC in Models with Universal Extra Dimensions

In this letter we study the process of gluon fusion into a pair of Higgs bosons in a model with one universal extra dimension. We find that the contributions from the extra top quark Kaluza-Klein excitations lead to a Higgs pair production cross section at the LHC that can be significantly altered compared to the Standard Model value for small values of the compactification scale.Comment: 10 pages, 6 figures. LHC cross section computed, 2 new figure

Higgs Up-Down CP Asymmetry at the LHC

We propose a new observable designed to probe CP-violating coupling of the Higgs boson to W bosons using associated Higgs production. We define an asymmetry that measures the number of leptons from W decays relative to the plane defined by the beam line and the Higgs boson momentum. The orientation of that plane is determined by the direction of fermions in the initial state, so that in a proton-proton collider it requires rapidity cuts that preferentially select quarks over antiquarks.Comment: 7 pages, 3 figure

On Composite Two Higgs Doublet Models

We investigate composite two Higgs doublet models realized as pseudo Goldstone modes, generated through the spontaneous breaking of a global symmetry due to strong dynamic at the TeV scale. A detailed comparative survey of two possible symmetry breaking patterns, SU(5) -> SU(4) x U(1) and SU(5) x SU(4), is made. We point out choices for the Standard Model fermion representations that can alleviate some phenomenological constraints, with emphasis towards a simultaneous solution of anomalous Zb\bar{b} coupling and Higgs mediated Flavor Changing Neutral Currents. We also write down the kinetic lagrangian for several models leading to Two Higgs Doublets and identify the anomalous contributions to the T parameter. Moreover, we describe a model based on the breaking $SO(9)/SO(8)$ in which there is no tree-level breaking of custodial symmetry, discussing also the possible embeddings for the fermion fields.Comment: 17 pages. Mistake corrected, added one section on a T- and flavor safe model based on SO(9)/SO(8). Matches published versio

Radion-Higgs mixing effects on bounds from LHC Higgs Searches

The radion, a scalar particle associated with the radius of a compact warped extra dimension, may be the lightest new particle in this class of models. Its couplings to SM particles are not very different from the usual Higgs boson. One of the main differences is the coupling to massless gauge bosons that receives contribution from the trace anomaly of the energy-momentum tensor due to the the nonvanishing $\beta$ functions. We use current LHC data on Higgs searches to find exclusion regions on the parameters of a radion model, paying particular attention to its mixing with the Higgs boson arising from a nonminimal coupling to gravity parametrized by a dimensionless coeficient $\xi$. We also comment on the interesting possibility of hiding the Higgs boson from the current searches in this model.The radion, a scalar particle associated with the radius of a compact warped extra dimension, may be the lightest new particle in this class of models. Its couplings to SM particles are proportional to the their masses, similar to the usual Higgs boson, but suppressed by a scale $\Lambda_r$, the radion vacuum expectation value. The main differences are the coupling to massless gauge bosons that receives contribution from the trace anomaly of the energy-momentum tensor due to the the nonvanishing $\beta$ functions and the mixing with the Higgs boson arising from a nonminimal coupling to gravity parametrized by a dimensionless coefficient $\xi$. In particular, these differences can result in significant modifications of the radion phenomenology.We use current LHC data on Higgs searches to find exclusion regions on the parameters of a radion model, $\Lambda_r$, $\xi$ and the radion mass $m_r$. We find that, even for low values of $\Lambda_r$, the radion can still have a mass in the region where the Standard Model Higgs has been excluded, for a narrow range of values for the mixing parameter. Some signals at the LHC for this scenario are discussed.We also find that it is possible to hide the Higgs boson in the current searches in this model, due to a suppression of its couplings