Eduardo Ponton

Realistic anomaly mediated supersymmetry breaking

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. Gaugino and scalar masses are naturally of the same order, and flavor-changing neutral currents are automatically suppressed. The most glaring problem with this scenario is that slepton masses are negative in the minimal supersymmetric standard model. We point out that this problem can be simply solved by coupling extra Higgs doublets to the leptons. Lepton flavor-changing neutral currents can be naturally avoided by approximate symmetries. We also describe more speculative solutions involving compositeness near the weak scale. We then turn to electroweak symmetry breaking. Adding an explicit μ term gives a value for Bμ that is too large by a factor of ~ 100. We construct a realistic model in which the μ term arises from the vacuum expectation value of a singlet field, so all weak-scale masses are directly related to m3/2. We show that fully realistic electroweak symmetry breaking can occur in this model with moderate fine-tuning.

Precision electroweak data and unification of couplings in warped extra dimensions

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. Moreover, the propagation of fermions in the bulk allows for a simple solution to potentially dangerous proton decay problems. However, bulk gauge fields and fermions pose a phenomenological challenge, since they tend to induce large corrections to the precision electroweak observables. In this article, we study in detail the effect of gauge and fermion fields propagating in the bulk in the presence of gauge brane kinetic terms compatible with gauge coupling unification, and we present ways of obtaining a consistent description of experimental data, while allowing values of the first Kaluza Klein mode masses of the order of a few TeV.

Electroweak phase transition, Higgs diphoton rate, and new heavy fermions

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.

Effective Lagrangians and light gravitino phenomenology

We construct the low-energy effective Lagrangian for a light gravitino coupled to the fields of the minimal supersymmetric standard model with soft supersymmetry breaking. Our effective Lagrangian is written in terms of the spin-

BMSSM Higgs Bosons at the Tevatron and the LHC

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Beyond the MSSM Higgs bosons at the 7 TeV LHC

Goldstino (the longitudinal component of the gravitino) transforming under a nonlinear realization of supersymmetry. The Goldstino is derivatively coupled. We use this Lagrangian to place bounds on the supersymmetry-breaking scale

GUT scale and superpartner masses from anomaly mediated supersymmetry breaking

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Dynamical determination of the unification scale by gauge-mediated supersymmetry breaking

from astrophysics, cosmology, and particle physics. The leading interactions of the Goldstino at low energies arise from Fayet-Iliopoulos terms induced by supersymmetry breaking, which give rise to a coupling of a single photon or

Gaugino mediated supersymmetry breaking

Z

A critical cosmological constant from millimeter extra dimensions

to Goldstino pairs. We argue that it is unnatural for the induced Fayet-Iliopoulos term to have a coefficient much less than