We demonstrate that flavor symmetries in warped geometry can provide a natural explanation for large mixing angles and economically explain the distinction between the quark and lepton flavor sectors. We show how to naturally generate Majorana neutri
no masses assuming a gauged a U(1)_{B-L} symmetry broken in the UV that generates see-saw masses of the right size. This model requires lepton minimal flavor violation (LMFV) in which only Yukawa matrices (present on the IR brane) break the flavor symmetries. The symmetry-breaking is transmitted to charged lepton bulk mass parameters as well to generate the hierarchy of charged lepton masses. With LMFV, a GIM-like mechanism prevents dangerous flavor-changing processes for charged leptons and permits flavor-changing processes only in the presence of the neutrino Yukawa interaction and are therefore suppressed when the overall scale for the neutrino Yukawa matrix is slightly smaller than one in units of the curvature. In this case the theory can be consistent with a cutoff of 10 TeV and 3 TeV Kaluza-Klein masses.
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. Here we consider neutral TeV-mass scalar dark matter, its necessary interactions, and potential signals. We consider signals both with and without higher-dimension operators generated by strong coupling at the TeV scale, as might happen for example in an RS scenario. We find some potential for detection in high energy photons that depends on the dark matter distribution. Detection in positrons at lower energies, such as those PAMELA probes, would be difficult though a higher energy positron signal could in principle be detectable over background. However, a light dark matter particle with higher-dimensional interactions consistent with a TeV cutoff can in principle match PAMELA data.
New resonances with masses of order a few ${rm TeV}$ might be discovered at the LHC. We show that no resonance that couples to electrons only through Standard Model interactions can decay to both $e^+e^-$and $gamma gamma$ with significant branching r
atios. This means that finding both electron-positron and two-photon final states is evidence that electrons couple directly to the new physics associated with the resonance and furthermore that the resonance is not spin-1. The least fine-tuned such examples involve electron compositeness. One such example, Kaluza Klein excitations of the graviton in the version of the Randall Sundrum Model where Standard Model matter is located on the ${rm TeV}$ brane, can be distinguished from other possibilities by its predicted branching fractions into the two modes.
We study two Higgs models for large $tanbeta$ and relatively large second Higgs mass. In this limit the second heavy Higgs should have small vev and therefore couples only weakly to two gauge bosons. Furthermore, the couplings to down type quarks can
be significantly modified (so long as the second Higgs is not overly heavy). Both these facts have significant implications for search strategies at the LHC and ILC. We show how an effective theory and explicit fundamental two Higgs model approach are related and consider the additional constraints in the presence of supersymmetry or $Z_2$ flavor symmetries. We argue that the best tests of the two Higgs doublet potential are likely to be measurements of the light Higgs branching fractions. We show how higher dimension operators that have recently been suggested to raise the light Higgs mass are probably best measured and distinguished in this way.
We present a variant of the warped extra dimension, Randall-Sundrum (RS), framework which is based on five dimensional (5D) minimal flavor violation (MFV), in which the only sources of flavor breaking are two 5D anarchic Yukawa matrices. The Yukawa m
atrices also control the bulk masses, which are responsible for the resulting flavor structure and mass hierarchy in the low energy theory. An interesting result of this set-up is that at low energies the theory flows to next to MFV model where flavor violation is dominantly coming from the third generation. Low energy flavor violation is further suppressed by a single parameter that dials the amount of violation in the up or down sector. There is therefore a sharp limit in which there is no flavor violation in the down type quark sector which, remarkably, is favored when we fit for the flavor parameters. This mechanism is used to eliminate the current RS flavor and CP problem even with a Kaluza-Klein scale as low as 2 TeV! Our construction also suggests that economic supersymmetric and non-supersymmetric, strong dynamic-based, flavor models may be built based on the same concepts.
We argue that the highly studied black hole signatures based on thermal multiparticle final states are very unlikely and only occur in a very limited parameter regime if at all. However, we show that if the higher-dimensional quantum gravity scale is
low, it should be possible to study quantum gravity in the context of higher dimensions through detailed compositeness-type searches.
