Even tiers and resonances on the Real Projective Plane

In this work we focus on various phenomenological aspects of the lightest even tiers, (2,0) and (0,2), in models based on a Real Projective Plane in 6 dimensions. We discuss the spectrum of the levels due to loop corrections, and the limit when the two radii are equal, in which case the two levels mix with each other and a new basis is defined. We also discuss the dependence of the spectrum on the ratio of the two radii. These results are essential to understand the phenomenology of the model at colliders (LHC) and to predict the relic abundance of Dark Matter. Finally, we estimate the bounds on the radius from resonant decays of the even tiers at the LHC, showing that they can be in the 600 GeV range after the complete analysis of the 2011 data.Comment: 43 pages, 10 figure

The Unhiggs

We examine a scenario where the Higgs is part of an approximate conformal field theory, and has a scaling dimension greater than one. Such an unparticle Higgs (or Unhiggs) can still break electroweak symmetry and unitarize WW scattering, but its gauge couplings are suppressed. An Unhiggs model has a reduced sensitivity of the weak scale to the cutoff, and can thus provide a solution to the little hierarchy problem.Comment: 21 pages, 9 figures; v2: further discussion, references added, version published in JHE

Continuum Superpartners

In an exact conformal theory there is no particle. The excitations have continuum spectra and are called "unparticles" by Georgi. We consider supersymmetric extensions of the Standard Model with approximate conformal sectors. The conformal symmetry is softly broken in the infrared which generates a gap. However, the spectrum can still have a continuum above the gap if there is no confinement. Using the AdS/CFT correspondence this can be achieved with a soft wall in the warped extra dimension. When supersymmetry is broken the superpartners of the Standard Model particles may simply be a continuum above gap. The collider signals can be quite different from the standard supersymmetric scenarios and the experimental searches for the continuum superpartners can be very challenging.Comment: 15 pages, 5 figures, talk at SCGT09 Workshop, Nagoya, Japan, 8-11 Dec, 200

Model Independent Framework for Searches of Top Partners

We propose a model-independent and general framework to study the LHC phenomenology of top partners, i.e. Vector-Like quarks including particles with different electro-magnetic charge. We consider Vector-Like quarks embedded in general representations of the weak SU(2)L, coupling to all Standard Model quarks via Yukawa mixing focusing on the case of a single multiplet. We show that, with very minimal and quite general assumptions, top partners may be studied in terms of few parameters in an effective Lagrangian description with a clear and simple connection with experimental observables. We also demonstrate that the parametrisation can be applied as well to cases with many Vector-like multiplets, thus covering most realistic models of New Physics. We perform a numerical study to understand the conclusions which can be drawn within such a description and the expected potential for discovery or exclusion at the LHC. Our main results are a clear connection between branching ratios and single production channels, and the identification of novel interesting channels to be studied at the LHC.Comment: 42 pages, 2 figures, 20 tables, added an appendix with a discussion of coupling chirality in general scenarios; added a comparison of collider and flavour bounds; added details about the range of validity of the framework. References adde

Electroweak Precision Observables and the Unhiggs

We compute one-loop corrections to the S and T parameters in the Unhiggs scenario. In that scenario, the Standard Model Higgs is replaced by a non-local object, called the Unhiggs, whose spectral function displays a continuum above the mass gap. The Unhiggs propagator has effectively the same UV properties as the Standard Model Higgs propagator, which implies that loop corrections to the electroweak precision observables are finite and calculable. We show that the Unhiggs is consistent with electroweak precision tests when its mass gap is at the weak scale; in fact, it then mimics a light SM Higgs boson. We also argue that the Unhiggs, while being perfectly visible to electroweak precision observables, is invisible to detection at LEP.Comment: 13 pages; v2: references added, discussion of production cross-section expande

Fundamental Composite (Goldstone) Higgs Dynamics

31 pagesWe provide a unified description, both at the effective and fundamental Lagrangian level, of models of composite Higgs dynamics where the Higgs itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudo-Goldstone boson or as a massive excitation of the condensate. We show that, in general, these states mix with repercussions on the electroweak physics and phenomenology. Our results will help clarify the main differences, similarities, benefits and shortcomings of the different ways one can naturally realize a composite nature of the electroweak sector of the Standard Model. We will analyze the minimal underlying realization in terms of fundamental strongly coupled gauge theories supporting the flavor symmetry breaking pattern SU(4)/Sp(4) $\sim$ SO(6)/SO(5). The most minimal fundamental description consists of an SU(2) gauge theory with two Dirac fermions transforming according to the fundamental representation of the gauge group. This minimal choice enables us to use recent first principle lattice results to make the first predictions for the massive spectrum for models of composite (Goldstone) Higgs dynamics. These results are of the upmost relevance to guide searches of new physics at the Large Hadron Collider

The AdS/CFT/Unparticle Correspondence

We examine the correspondence between the anti-de Sitter (AdS) description of conformal field theories (CFTs) and the unparticle description of CFTs. We show how unparticle actions are equivalent to holographic boundary actions for fields in AdS, and how massive unparticles provide a new type of infrared cutoff that can be simply implemented in AdS by a soft breaking of conformal symmetry. We also show that processes involving scalar unparticles with dimensions d_s<2 or fermion unparticles with dimensions d_f<5/2 are insensitive to ultraviolet cutoff effects. Finally we show that gauge interactions for unparticles can be described by bulk gauge interactions in AdS and that they correspond to minimal gauging of the non-local effective action, and we compute the fermion unparticle production cross-section.Comment: 26 pages, 1 figur

The Minimal Set of Electroweak Precision Parameters

We present a simple method for analyzing the impact of precision electroweak data above and below the Z-peak on flavour-conserving heavy new physics. We find that experiments have probed about ten combinations of new physics effects, which to a good approximation can be condensed into the effective oblique parameters Shat, That, Uhat, V, X, W, Y (we prove positivity constraints W, Y >= 0) and three combinations of quark couplings (including a distinct parameter for the bottom). We apply our method to generic extra Z' vectors.Comment: 22 pages, 3 figure