E. Ponton - Yale University

E. Ponton
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Name
E. Ponton
Affiliation
Yale University
City
New Haven
Country
United States

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High Energy Physics - Phenomenology (47)
 
High Energy Physics - Theory (14)
 
Cosmology and Nongalactic Astrophysics (2)
 
High Energy Physics - Experiment (1)
 
High Energy Astrophysical Phenomena (1)
 
Astrophysics (1)

Publications Authored By E. Ponton

The radial excitation of the global symmetry-breaking vacuum in composite Higgs models, called the "global Higgs", has been recently a focus of investigation. In this paper we study the prospects for detecting this composite scalar at the 13 TeV LHC. We compute the global Higgs production rates and estimate the discovery potential of a global Higgs decaying into top quark pairs and into Higgs and electroweak gauge bosons with subsequent hadronic decays. Read More

We consider scenarios of Higgs compositeness where the Higgs doublet arises as a pseudo-Nambu Goldstone boson. Our focus is the physical scalar ("radial") excitation associated with the global symmetry breaking vacuum, which we call the "global Higgs". For the minimal case of a $SO(5)/SO(4)$ coset, the couplings of the global Higgs to Standard Model (SM) particles are fully determined by group theoretical factors and two decay constants. Read More

We present a simple microscopic realization of a pseudo-Nambu-Goldstone (pNGB) boson Higgs scenario arising from the breaking of $SO(5) \rightarrow SO(4)$. The Higgs constituents are explicitly identified as well as the interactions responsible for forming the bound state and breaking the electroweak symmetry. This outcome follows from the presence of four-fermion interactions with a super-critical coupling, and uses the Nambu-Jona-Lasinio mechanism to break the global $SO(5)$ symmetry. Read More

We study a supersymmetric scenario with a quasi exact R-symmetry in light of the discovery of a Higgs resonance with a mass of 125 GeV. In such a framework, the additional adjoint superfields, needed to give Dirac masses to the gauginos, contribute both to the Higgs mass and to electroweak precision observables. We analyze the interplay between the two aspects, finding regions in parameter space in which the contributions to the precision observables are under control and a 125 GeV Higgs boson can be accommodated. Read More

We consider composite Higgs models where the Higgs is a pseudo-Nambu Goldstone boson arising from the spontaneous breaking of an approximate global symmetry by some underlying strong dynamics. We focus on the SO(5) -> SO(4) symmetry breaking pattern, assuming the partial compositeness paradigm. We study the consequences on Higgs physics of the fermionic representations produced by the strong dynamics, that mix with the Standard Model (SM) degrees of freedom. Read More

We show that weak scale vector-like fermions with order one couplings to the Higgs can lead to a novel mechanism for a strongly first-order electroweak phase transition (EWPhT), through their tendency to drive the Higgs quartic coupling negative. These same fermions could also enhance the loop-induced branching fraction of the Higgs into two photons, as suggested by the recent discovery of a ~125 GeV Higgs-like state at the CERN Large Hadron Collider (LHC). Our results suggest that measurements of the diphoton decay rate of the Higgs and its self coupling, at the LHC or perhaps at a future lepton collider, could probe the EWPhT in the early Universe, with significant implications for the viability of electroweak baryogenesis scenarios. Read More

We perform a detailed study of a variety of LHC signals in supersymmetric models where lepton number is promoted to an (approximate) U(1)_R symmetry. Such a symmetry has interesting implications for naturalness, as well as flavor- and CP-violation, among others. Interestingly, it makes large sneutrino vacuum expectation values phenomenologically viable, so that a slepton doublet can play the role of the down-type Higgs. Read More

A classification of phenomenologically interesting supersymmetric extensions of the Standard-Model with a $U(1)_R$ symmetry is presented. Some of these are consistent with subsets of leptonic or baryonic "R-parity violating" (RPV) operators, thereby providing a natural motivation for them. We then focus on a particular class of models in which the $U(1)_R$ symmetry coincides with lepton number when restricted to the SM sector. Read More

Compact spatial dimension at the TeV scale remain an intriguing possibility that is currently being tested at the LHC. We give an introductory review of extra-dimensional models and ideas, from a phenomenological perspective, but emphasizing the appropriate theoretical tools. We emphasize the power and limitations of such constructions, and give a self-contained account of the methods necessary to understand the associated physics. Read More

We consider the Higgs sector in extensions of the Minimal Supersymmetric Standard Model by higher-dimension operators in the superpotential and the K\"ahler potential, in the context of Higgs searches at the LHC 7 TeV run. Such an effective field theory (EFT) approach, also referred to as BMSSM, allows for a model-independent description that may correspond to the combined effects of additional supersymmetric sectors, such as heavy singlets, triplets or gauge bosons, in which the supersymmetry breaking mass splittings can be treated as a perturbation. We consider the current LHC dataset, based on about $1-2 {\rm fb}^{-1}$ of data to set exclusion limits on a large class of BMSSM models. Read More

It is well known that R-symmetric models dramatically alleviate the SUSY flavor and CP problems. We study particular modifications of existing R-symmetric models which share the solution to the above problems, and have interesting consequences for electroweak baryogenesis and the Dark Matter (DM) content of the universe. In particular, we find that it is naturally possible to have a strongly first-order electroweak phase transition while simultaneously relaxing the tension with EDM experiments. Read More

We study the effect of bulk fermions on electroweak precision observables in a recently proposed model with warped extra dimensions and no custodial symmetry. We find that the top-quark mass, together with the corrections to the Zbb vertex and the one-loop contribution to the T parameter, which is finite, impose important constraints that single out a well defined region of parameter space. New massive vector bosons can be as light as 1. Read More

Warped scenarios offer an appealing solution to the hierarchy problem. We consider a non-trivial deformation of the basic Randall-Sundrum framework that has a KK-parity symmetry. This leads to a stable particle beyond the Standard Model, that is generically expected to be the first KK-parity odd excitation of the radion field. Read More

Anarchic warped extra dimensional models provide a solution to the hierarchy problem. They can also account for the observed flavor hierarchies, but only at the expense of little hierarchy and CP problems, which naturally require a Kaluza-Klein (KK) scale beyond the LHC reach. We have recently shown that when flavor issues are decoupled, and assumed to be solved by UV physics, the framework's parameter space greatly opens. Read More

We consider a 5D warped scenario with a KK-parity symmetry, where the non-trivial warping arises from the dynamics that stabilizes the size of the extra dimension. Generically, the lightest Kaluza-Klein (KK) particle is the first excitation of the radion field, while the next-to-lightest Kaluza-Klein particle is either the first excitation of the (RH) top quark or the first KK-parity odd Higgs. All these masses are expected to be of order the electroweak scale. Read More

In warped models that solve the hierarchy problem, there is generally no dynamical relation between the size of the fifth dimension and the scale of electroweak symmetry breaking (EWSB). The establishment of such a relation, without fine-tuning, requires that Casimir contributions to the radion potential not exceed the energy density associated with EWSB. Here, we examine the use of supersymmetry for controlling the Casimir energy density and making quantum contributions calculable. Read More

A warped extra-dimensional model, where the Standard Model Yukawa hierarchy is set by UV physics, is shown to have a sweet spot of parameters with improved experimental visibility and possibly naturalness. Upon marginalizing over all the model parameters, a Kaluza-Klein scale of 2.1 TeV can be obtained at 2 sigma (95. Read More

We consider extensions of the Minimal Supersymmetric Standard Model (MSSM) where the extra degrees of freedom interact weakly with the Higgs sector. These models allow to relax the tension between the lower bound on the lightest CP even Higgs mass from direct LEP searches and the theoretical upper bound of the MSSM. We study the beyond MSSM (BMSSM) effects via an effective field-theory approach, assuming that the MSSM is valid up to a heavy physics scale M. Read More

We study extensions of the Minimal Supersymmetric Standard Model (MSSM) with new degrees of freedom that couple sizably to the MSSM Higgs sector and lie in the TeV range. After integrating out the physics at the TeV scale, the resulting Higgs spectrum can significantly differ from typical supersymmetric scenarios, thereby providing a window Beyond the MSSM (BMSSM). Taking into account current LEP and Tevatron constraints, we perform an in-depth analysis of the Higgs collider phenomenology and explore distinctive characteristics of our scenario with respect to both the Standard Model and the MSSM. Read More

The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Read More

We consider supersymmetric models that include particles beyond the Minimal Supersymmetric Standard Model (MSSM) with masses in the TeV range, and that couple significantly to the MSSM Higgs sector. We perform a model-independent analysis of the spectrum and couplings of the MSSM Higgs fields, based on an effective theory of the MSSM degrees of freedom. The tree-level mass of the lightest CP-even state can easily be above the LEP bound of 114 GeV, thus allowing for a relatively light spectrum of superpartners, restricted only by direct searches. Read More

Warped 5-dimensional models, based on the original Randall-Sundrum geometry, have been extended beyond their initial purpose of resolving the gauge hierarchy problem. Over the past decade, various ingredients have been added to their basic structure in order to provide natural and predictive models of flavor and also to address existing constraints from precision data. In this review, we examine the theoretical and experimental status of realistic models that accommodate current data, while addressing the hierarchy and flavor puzzles of the Standard Model. Read More

We point out that the light radion phi in a recently proposed Warped Top-Condensation Model, can provide distinct signatures in b -> s phi, where the on-shell phi can decay with displaced vertices. We find that some of the parameter space of these models is constrained by B-meson and astrophysical data. Future B-decay measurements can lead to the discovery of the WTCM. Read More

It is well known that stable weak scale particles are viable dark matter candidates since the annihilation cross section is naturally about the right magnitude to leave the correct thermal residual abundance. Many dark matter searches have focused on relatively light dark matter consistent with weak couplings to the Standard Model. However, in a strongly coupled theory, or even if the coupling is just a few times bigger than the Standard Model couplings, dark matter can have TeV-scale mass with the correct thermal relic abundance. Read More

In the Minimal Supersymmetric Standard Model (the MSSM), the electroweak symmetry is restored as supersymmetry-breaking terms are turned off. We describe a generic extension of the MSSM where the electroweak symmetry is broken in the supersymmetric limit. We call this limit the "sEWSB" phase, short for supersymmetric electroweak symmetry breaking. Read More

We propose a scenario in which the Planck scale is dynamically linked to the electroweak scale induced by top condensation. The standard model field content, without the Higgs, is promoted to a 5D warped background. There is also an additional 5D fermion with the quantum numbers of the right-handed top. Read More

We show that a discrete exchange symmetry can give rise to realistic dark matter candidates in models with warped extra dimensions. We show how to realize our construction in a variety of models with warped extra dimensions and study in detail a realistic model of Gauge-Higgs Unification/composite Higgs in which the observed amount of dark matter is naturally reproduced. In this model, a realistic pattern of electroweak symmetry breaking typically occurs in a region of parameter space in which the fit to the electroweak precision observables improves, the Higgs is heavier than the experimental bound and new light quark resonances are predicted. Read More

It has been recently argued that realistic models with warped extra dimensions can have Kaluza-Klein particles accessible at the Large Hadron Collider if a custodial symmetry, SU(2)_V \times P_{LR}, is used to protect the T parameter and the coupling of the left-handed bottom quark to the Z gauge boson. In this article we emphasize that such a symmetry implies that the loop corrections to both the T parameter and the Z b_L \bar{b}_L coupling are calculable. In general, these corrections are correlated, can be sizable, and should be considered to determine the allowed parameter space region in models with warped extra dimensions and custodial symmetry, including Randall-Sundrum models with a fundamental Higgs, models of gauge-Higgs unification and Higgsless models. Read More

We consider Randall-Sundrum scenarios based on SU(2)_L x SU(2)_R and a discrete parity exchanging L with R. The custodial and parity symmetries can be used to make the tree level contribution to the T parameter and the anomalous couplings of the bottom quark to the Z very small. We show that the resulting quantum numbers typically induce a negative T parameter at one loop that, together with the positive value of the S parameter, restrict considerably these models. Read More

Standard model gauge bosons propagating in two universal extra dimensions give rise to heavy spin-1 and spin-0 particles. The lightest of these, carrying Kaluza-Klein numbers (1,0), may be produced only in pairs at colliders, whereas the (1,1) modes, which are heavier by a factor of \sqrt{2}, may be singly produced. We show that the cascade decays of (1,1) particles generate a series of closely-spaced narrow resonances in the t\bar{t} invariant mass distribution. Read More

We consider general field theories in six dimensions, with two of the dimensions compactified on a T_{2}/Z_{4} orbifold. Six-dimensional Weyl fermions propagating on this background give rise to a chiral zero-mode, which makes them interesting for phenomenological applications. The compact two-dimensional space is flat and has three conical singularities. Read More

We construct gauge theories in two extra dimensions compactified on the chiral square, which is a simple compactification that leads to chiral fermions in four dimensions. Stationarity of the action on the boundary specifies the boundary conditions for gauge fields. Any six-dimensional gauge field decomposed in Kaluza-Klein modes includes a tower of heavy spin-1 particles whose longitudinal polarizations are linear combinations of the extra-dimensional components, and a tower of heavy spin-0 particles corresponding to the orthogonal combinations. Read More

We analyze the behavior of Standard Model matter propagating in a slice of AdS_5 in the presence of infrared-brane kinetic terms. Brane kinetic terms are naturally generated through radiative corrections and can also be present at tree level. The effect of the brane kinetic terms is to expell the heavy KK modes from the infrared-brane, and hence to reduce their coupling to the localized Higgs field. Read More

We study quantum field theory in six dimensions with two of them compactified on a square. A simple boundary condition is the identification of two pairs of adjacent sides of the square such that the values of a field at two identified points differ by an arbitrary phase. This allows a chiral fermion content for the four-dimensional theory obtained after integrating over the square. Read More

Warped extra dimensions allow a novel way of solving the hierarchy problem, with all fundamental mass parameters of the theory naturally of the order of the Planck scale. The observable value of the Higgs vacuum expectation value is red-shifted, due to the localization of the Higgs field in the extra dimension. It has been recently observed that, when the gauge fields propagate in the bulk, unification of the gauge couplings may be achieved. Read More

We consider five dimensional supersymmetric warped scenarios in which the Standard Model quark and lepton fields are localized on the ultraviolet brane, while the Standard Model gauge fields propagate in the bulk. Supersymmetry is assumed to be broken on the infrared brane. The relative sizes of supersymmetry breaking effects are found to depend on the hierarchy between the infrared scale and the weak scale. Read More

We examine localized kinetic terms for gauge fields which can propagate into compact, warped extra dimensions. We show that these terms can have a relevant impact on the values of the Kaluza-Klein (KK) gauge field masses, wave functions, and couplings to brane and bulk matter. The resulting phenomenological implications are discussed. Read More

2002Jan
Affiliations: 1Yale University, 2Yale University, 3Yale University, 4Yale University

We examine the origin of neutrino masses and oscillations in the context of the six-dimensional standard model. The space-time symmetries of this model explain proton stability and forbid Majorana neutrino masses. The consistency of the six-dimensional theory requires three right-handed neutrinos, and therefore Dirac neutrino masses are allowed. Read More

We consider models which are natural extensions of those where supersymmetry is broken at low energy scales and transmitted to visible matter by gauge interactions. We investigate the situation where the quark and lepton superfields of the MSSM are localized to a brane in a higher dimensional space while the messenger fields and the sector which breaks supersymmetry dynamically are localized to another brane in the same space. The MSSM gauge and Higgs fields are assumed to propagate in the bulk. Read More

2001Jul

We show that Lorentz and gauge invariance explain the long proton lifetime within the standard model in six dimensions. The baryon-number violating operators have mass dimension 15 or higher. Upon TeV-scale compactification of the two universal extra dimensions on a square $T^2/Z_2$ orbifold, a discrete subgroup of the 6-dimensional Lorentz group continues to forbid dangerous operators. Read More

We compute the one-loop Casimir energy of gravity and matter fields, obeying various boundary conditions, in 5-dimensional S^1/Z_2 and 6-dimensional T^2/Z_k orbifolds. We discuss the role of the Casimir energy in possible radius stabilization mechanisms and show that the presence of massive as well as massless fields can lead to minima with zero cosmological constant. In the 5-d orbifold, we also consider the case where kinetic terms localized at the fixed points are not small. Read More

We study the localization of gravity on string-like defects in codimension two. We point out that the gravity-localizing `local cosmic string' spacetime has an orbifold singularity at the horizon. The supergravity embedding and the AdS/CFT correspondence suggest ways to resolve the singularity. Read More

We consider models of anomaly-mediated supersymmetry breaking (AMSB) in which the grand unification (GUT) scale is determined by the vacuum expectation value of a chiral superfield. If the anomaly-mediated contributions to the potential are balanced by gravitational-strength interactions, we find a model-independent prediction for the GUT scale of order $M_{\rm Planck} / (16\pi^2)$. The GUT threshold also affects superpartner masses, and can easily give rise to realistic predictions if the GUT gauge group is asymptotically free. Read More

We consider `brane universe' scenarios with standard-model fields localized on a 3-brane in 6 spacetime dimensions. We show that if the spacetime is rotationally symmetric about the brane, local quantities in the bulk are insensitive to the couplings on the brane. This potentially allows compactifications where the effective 4-dimensional cosmological constant is independent of the couplings on the 3-brane. Read More

We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a "3-brane" in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane, supersymmetry breaking is communicated to gauge and Higgs fields by direct higher-dimension interactions, and to quark and lepton fields via standard-model loops. We show that this gives rise to a realistic and predictive model for supersymmetry breaking. Read More

We consider theories with one or more compact dimensions with size r > 1/M, where M is the fundamental Planck scale, with the visible and hidden sectors localized on spatially separated "3-branes." We show that a bulk U(1) gauge field spontaneously broken on the hidden-sector 3-brane is an attractive candidate for the messenger of supersymmetry breaking. In this scenario scalar mass-squared terms are proportional to U(1) charges, and therefore naturally conserve flavor. Read More

We consider supersymmetry breaking communicated entirely by the superconformal anomaly in supergravity. This scenario is naturally realized if supersymmetry is broken in a hidden sector whose couplings to the observable sector are suppressed by more than powers of the Planck scale, as occurs if supersymmetry is broken in a parallel universe living in extra dimensions. This scenario is extremely predictive: soft supersymmetry breaking couplings are completely determined by anomalous dimensions in the effective theory at the weak scale. Read More

We consider models of dynamical supersymmetry breaking in which the extremization of a tree-level superpotential conflicts with a quantum constraint. We show that in such models the low-energy effective theory near the origin of moduli space is an O'Raifeartaigh model, and the sign of the mass-squared for the pseudo-flat direction at the origin is calculable. We analyze vector-like models with gauge groups SU(N) and Sp(2N) with and without global symmetries. Read More

We propose a mechanism for generating the GUT scale dynamically from the Planck scale. The idea is that the GUT scale is fixed by the vacuum expectation value of a "GUT modulus" field whose potential is exactly flat in the supersymmetric limit. If supersymmetry is broken by gauge mediation, a potential for the GUT modulus is generated at 2 loops, and slopes away from the origin for a wide range of parameters. Read More

We construct the low-energy effective lagrangian for a light gravitino coupled to the minimal supersymmetric standard model under the assumption that supersymmetry breaking is communicated to the observable sector dominantly through soft terms. Our effective lagrangian is written in terms of the spin-1/2 Goldstino (the longitudinal component of the gravitino) transforming under a non-linear realization of supersymmetry. In this lagrangian, the Goldstino is derivatively coupled and all couplings of the Goldstino to light fields are determined uniquely by the supersymmetry-breaking scale \sqrt{F}. Read More