Natural models of supersymmetry with a gravitino LSP provide distinctive signatures at the LHC. For a neutralino NLSP, sparticles can decay to two high energy photons plus missing energy. We use the ATLAS diphoton search with 4.8 fb^{-1} of data to p
lace limits in both the stop-gluino and neutralino-chargino mass planes for this scenario. If the neutralino is heavier than 50 GeV, the lightest stop must be heavier than 580 GeV, the gluino heavier than 1100 GeV and charginos must be heavier than approximately 300-470 GeV. This provides the first nontrivial constraints in natural gauge mediation models with a neutralino NLSP decaying to photons, and implies a fine tuning of at least a few percent in such models.
We show that when supersymmetry is broken at the TeV scale by strong dynamics, the Higgs sector of the MSSM can be drastically modified. This arises from possible sizeable mixings of the Higgs with the resonances of the strong sector. In particular t
he mass of the lightest Higgs boson can be significantly above the MSSM bound (~130 GeV). Furthermore only one Higgs doublet is strictly necessary, because the Yukawa couplings can have a very different structure compared to the MSSM. Using the AdS/CFT correspondence electroweak precision observables can be calculated and shown to be below experimental bounds. The most natural way to generate sparticle masses is through mixing with the composite states. This causes the gauginos and Higgsinos to easily obtain Dirac masses around 200 GeV, while scalar masses can be generated either from extra D-terms or also through mixing with the strongly-coupled states. Finally one of the most interesting predictions of these scenarios is the sizeable decay width of the Higgs boson into a very light gravitino (~ 10^{-4} eV) and a Higgsino.
We provide an introduction to the physics of a warped extra dimension and the AdS/CFT correspondence. An AdS/CFT dictionary is given which leads to a 4D holographic view of the 5th dimension. With a particular emphasis on beyond the standard model ph
ysics, this provides a window into the strong dynamics associated with either electroweak symmetry breaking or supersymmetry breaking. In this way hierarchies associated with either the electroweak or supersymmetry breaking scale, together with the fermion mass spectrum, can be addressed in a consistent framework.
The formalism for modeling multiple fermion generations in a warped extra dimension with a soft-wall is presented. A bulk Higgs condensate is responsible for generating mass for the zero-mode fermions but leads to additional complexity from large mix
ing between different flavors. We extend existing single-generation analyses by considering new special cases in which analytical solutions can be derived and discuss flavor constraints. The general three-generation case is then treated using a simple numerical routine. Assuming anarchic 5D parameters we find a fermion mass spectrum resembling the standard model quarks and leptons with highly degenerate couplings to Kaluza-Klein gauge bosons. This confirms that the soft-wall model has similar attractive features as that found in hard-wall models, providing a framework to generalize existing phenomenological analyses.
We present a model of electroweak symmetry breaking in a warped extra dimension where electroweak symmetry is broken at the UV (or Planck) scale. An underlying conformal symmetry is broken at the IR (or TeV) scale generating masses for the electrowea
k gauge bosons without invoking a Higgs mechanism. By the AdS/CFT correspondence the W,Z bosons are identified as composite states of a strongly-coupled gauge theory, suggesting that electroweak symmetry breaking is an emergent phenomenon at the IR scale. The model satisfies electroweak precision tests with reasonable fits to the S and T parameter. In particular the T parameter is sufficiently suppressed since the model naturally admits a custodial SU(2) symmetry. The composite nature of the W,Z-bosons provide a novel possibility of unitarizing WW scattering via form factor suppression. Constraints from LEP and the Tevatron as well as discovery opportunities at the LHC are discussed for these composite electroweak gauge bosons.
