Pseudo-Familon Dark Matter

Motivated by a model of pseudo-Majoron dark matter, we show how the breaking of a global symmetry that acts nontrivially in lepton generation space can lead to a viable pseudo-familon dark matter candidate. Unlike the pseudo-Majoron, the pseudo-familon in our model decays primarily to charged leptons and can account for the excess observed in the cosmic ray electron and positron spectra.Comment: 12 pages LaTeX, 1 figur

Orbitally Excited Baryons in Large N_c QCD

We present a model-independent analysis of the mass spectrum of nonstrange l=1 baryons in large N_c QCD. The 1/N_c expansion is used to select and order a basis of effective operators that spans the nine observables (seven masses and two mixing angles). Comparison to the data provides support for the validity of the 1/N_c expansion, but also reveals that only a few nontrivial operators are strongly preferred. We show that our results have a consistent interpretation in a constituent quark model with pseudoscalar meson exchange interactions.Comment: 4 pages LaTeX. Invited parallel session talk presented at the XVth Particles and Nuclei International Conference (PANIC99), June 10, 1999, Uppsala, Swede

A Peculiar Dynamically Warped Theory Space

We study a supersymmetric deconstructed gauge theory in which a warp factor emerges dynamically, driven by Fayet-Iliopoulos terms. The model is peculiar in that it possesses a global supersymmetry that remains unbroken despite nonvanishing D-term vacuum expectation values. Inclusion of gravity and/or additional messenger fields leads to the collective breaking of supersymmetry and to an unusual phenomenology.Comment: 4 pages LaTeX, Presented at SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, Irvine, California, USA 12-17 June 200

Electroweak Constraints on Extended Models with Extra Dimensions

Electroweak measurements place significant bounds on higher-dimensional versions of the standard model in which the gauge and Higgs fields have Kaluza-Klein excitations. These bounds may be altered quantitatively if chiral matter is also allowed to propagate in the higher-dimensional `bulk'. We determine the electroweak constraints on a number of models of this type, including scenarios in which only the leptons or only the first two generations of matter fields propagate in the bulk. We also consider the possibility that different factors of the electroweak gauge group may be distinguished by their bulk/three-brane assignment, and study a minimal extra-dimensional Z' model. We find typical bounds on the compactification scale between 1.5 and 4 TeV, and comment on models in which these bounds might be significantly relaxed.Comment: 15 pages Revtex, 1 EPS figur

U(2) Flavor Physics without U(2) Symmetry

We present a model of fermion masses based on a minimal, non-Abelian discrete symmetry that reproduces the Yukawa matrices usually associated with U(2) theories of flavor. Mass and mixing angle relations that follow from the simple form of the quark and charged lepton Yukawa textures are therefore common to both theories. We show that the differing representation structure of our horizontal symmetry allows for new solutions to the solar and atmospheric neutrino problems that do not involve modification of the original charged fermion Yukawa textures, or the introduction of sterile neutrinos.Comment: 12 pages RevTeX, 1 eps figure. A few typos correcte

Bounds on Bosonic Topcolor

We consider the phenomenology of models in which electroweak symmetry breaking is triggered by new strong dynamics affecting the third generation and is transmitted to the light fermions via a fundamental Higgs doublet. While similar in spirit to the old bosonic technicolor idea, such `bosonic topcolor' models are allowed by current phenomenological constraints, and may arise naturally in models with large extra dimensions. We study the parameter space of a minimal low-energy theory, including bounds from Higgs boson searches, precision electroweak parameters, and flavor changing neutral current processes. We show that the model can provide a contribution to D0-D0-bar mixing as large as the current experimental bound.Comment: 16 pages RevTeX, 3 Figure

TeV Right-handed Neutrinos and the Flavor-symmetry-improved Seesaw Mechanism

Horizontal flavor symmetries can drastically suppress Dirac neutrino masses well below those of the corresponding charged leptons. We show that models can be constructed where the light neutrino mass eigenvalues are small enough to give the MSW solution to the solar neutrino problem, with a right-handed neutrino scale no larger than a TeV. We present a model of this type where the right-handed neutrino scale is generated by the spontaneous breakdown of gauged U(1)$_{B-L}$, in a radiative breaking scenario driven by the right-handed neutrino Yukawa couplings. The model allows for a solution to the $\mu$ problem, and predicts the existence of a $Z'$ boson within the reach of the LHC or the Tevatron.Comment: 16 pp. LaTe