A few possible explanations of physics beyond the Standard Model

Weak scale supersymmetry provides elegant solutions to many of the problems of the standard model, but it also generically gives rise to excessive flavor and CP violation. I show that if the mechanism that suppresses the Yukawa couplings also suppresses flavor changing interactions in the supersymmetry breaking parameters, essentially all the low energy flavor and CP constraints can be satisfied. The standard assumption of flavor universality in the supersymmetry breaking sector is not necessary. I also study signatures of this framework at the LHC. The mass splitting among different generations of squarks and sleptons can be much larger than in conventional scenarios, and even the mass ordering can be changed. I find that there is a plausible scenario in which the NLSP is a long-lived right-handed selectron or smuon decaying into the LSP gravitino. This leads to the spectacular signature of monochromatic electrons or muons in a stopper detector, providing strong evidence for the framework.;I also present concrete realizations of this framework in higher dimensions. The Higgs fields and the supersymmetry breaking field are localized in the same place in the extra dimension(s). The Yukawa couplings and operators generating the supersymmetry breaking parameters then receive the same suppression factors from the wavefunction profiles of the matter fields, leading to a specific correlation between these two classes of interactions. I construct both unified and non-unified models in this framework, which can be either strongly or weakly coupled at the cutoff scale. I analyze one version in detail, a strongly coupled unified model, which addresses various issues of supersymmetric grand unification. The models presented here provide an explicit example in which the supersymmetry breaking spectrum can be a direct window into the physics of flavor at a very high energy scale.;I also study, in an operator analysis, the compatibility between low energy flavor and CP constraints and observability of superparticles at the LHC, assuming a generic correlation between the Yukawa couplings and the supersymmetry breaking parameters. I find that the superpotential operators that generate scalar trilinear interactions are generically problematic. I discuss several ways in which this tension is naturally avoided. In particular, I focus on several frameworks in which the dangerous operators are naturally absent. These frameworks can be combined with many theories of flavor, including those with (flat or warped) extra dimensions, strong dynamics, or flavor symmetries. I show that the resulting theories can avoid all the low energy constraints while keeping the superparticles light. The intergenerational mass splittings among the sfermions can reflect the structure of the underlying flavor theory, and can be large enough to be measurable at the LHC. Detailed observations of the superparticle spectrum may thus provide new handles on the origin of the flavor structure of the standard model.;Independent of supersymmetry, I also study the electron/positron excesses seen by PAMELA and ATIC. One interpretation of these excesses is dark matter annihilation in the galactic halo. Depending on the annihilation channel, the electron/positron signal could be accompanied by a galactic gamma ray or neutrino flux, and the non-detection of such fluxes constrains the couplings and halo properties of dark matter. I study the interplay of electron data with gamma ray and neutrino constraints in the context of cascade annihilation models, where dark matter annihilates into light degrees of freedom which in turn decay into leptons in one or more steps. Electron and muon cascades give a reasonable fit to the PAMELA and ATIC data. Compared to direct annihilation, cascade annihilations can soften gamma ray constraints from final state radiation by an order of magnitude. However, if dark matter annihilates primarily into muons, the neutrino constraints are robust regardless of the number of cascade decay steps. I also examine the electron data and gamma ray/neutrino constraints on the recently proposed "axion portal" scenario.