The Strongly-Interacting Light Higgs

We develop a simple description of models where electroweak symmetry breaking is triggered by a light composite Higgs, which emerges from a strongly-interacting sector as a pseudo-Goldstone boson. Two parameters broadly characterize these models: m_rho, the mass scale of the new resonances and g_rho, their coupling. An effective low-energy Lagrangian approach proves to be useful for LHC and ILC phenomenology below the scale m_rho. We identify two classes of operators: those that are genuinely sensitive to the new strong force and those that are sensitive to the spectrum of the resonances only. Phenomenological prospects for the LHC and the ILC include the study of high-energy longitudinal vector boson scattering, strong double-Higgs production and anomalous Higgs couplings. We finally discuss the possibility that the top quark could also be a composite object of the strong sector.Comment: 45 pages, 1 figure. v2: references adde

Brane Cosmology and KK Gravitinos

The cosmology of KK gravitinos in models with extra dimensions is considered. The main result is that the production of such KK modes is not compatible with an epoch of non--standard expansion after inflation. This is so because the BBN constraint on the zero mode forces the reduced five dimensional Planck mass $M_5$ down to values much smaller than the usual four dimensional one, but this in turn implies many KK states available for a given temperature. Once these states are taken into account one finds that there is no $M_5$ for which the produced KK gravitinos satisfy BBN and overclosure constraints. This conclusion holds for both flat and warped models in which only gravity propagates in the full spacetime.Comment: 19 pages, references added, IoP styl

Unusual Higgs or Supersymmetry from Natural Electroweak Symmetry Breaking

This review provides an elementary discussion of electroweak symmetry breaking in the minimal and the next-to-minimal supersymmetric models with the focus on the fine-tuning problem -- the tension between natural electroweak symmetry breaking and the direct search limit on the Higgs boson mass. Two generic solutions of the fine-tuning problem are discussed in detail: models with unusual Higgs decays; and models with unusual pattern of soft supersymmetry breaking parameters.Comment: 23 pages, 6 figures; invited review by MPL

Recurrent respiratory infections between immunity and atopy

Recurrent respiratory infections (RRIs) are frequent in children and are characterized by more than 6 airway infections in 1 year or more than 1 upper airway infection per month in the period between September and April or more than 3 lower airway infections in 1 year. Often pediatric RRIs are related to predisposing factors, such as reduced airway size, poor tussive reflex, and immaturity of the immune system. RRIs due to immature immune system are a transient condition, with spontaneous resolution in the school age. However, some RRIs are expression of more complex diseases. Red flags are the onset of symptoms in the first year of life, the involvement of other systems, unusual pathogens, slowing of growth, severe infections of the lower airways, and recurrence of the infection site. To help the pediatrician in the RRI differential diagnosis, we have created a roadmap based on scientific literature data and clinical practice that identifies 6 macro areas: immunodeficiencies, simple minimal genetic immunodeficiency, atopy, obesity, nutritional deficiencies, autoinflammatory diseases, and complex diseases

Loop-Effects in Pseudo-Supersymmetry

We analyze the transmission of supersymmetry breaking in brane-world models of pseudo-supersymmetry. In these models two branes preserve different halves of the bulk supersymmetry. Thus supersymmetry is broken although each sector of the model is supersymmetric when considered separately. The world-volume theory on one brane feels the breakdown of supersymmetry only through two-loop interactions involving a coupling to fields from the other brane. In a 5D toy model with bulk vectors, we compute the diagrams that contribute to scalar masses on one brane and find that the masses are proportional to the compactification scale up to logarithmic corrections, m^2 ~ (2 pi R)^{-2}(ln(2 pi R ms)-1.1), where ms is an ultraviolet cutoff. Thus, for large compactification radii, where this result is valid, the brane scalars acquire a positive mass squared. We also compute the three-loop diagrams relevant to the Casimir energy between the two branes and find E ~ (2 pi R)^{-4}((ln(2 pi R ms)-1.7)^2+0.2). For large radii, this yields a repulsive Casimir force.Comment: Latex, 30 pages, 6 figures, v2: minor corrections, comments on susy algebra and x^5 covariant derivative adde

Composite MFV and Beyond

We revisit and extend realizations of Minimal Flavor Violation (MFV) in theories with strongly coupled electro-weak symmetry breaking. MFV requires that some chiralities of light SM quarks are strongly composite leading, depending on the scenario, to bounds from compositeness searches, precision electro-weak tests or even flavor physics. Within the framework of partial compositeness we show how to extend the MFV paradigm allowing the treat the top quark differently. This can be realized if for example the strong sector has an U(2) symmetry. In this case the light generations can be mostly elementary and all the bounds are easily satisfied.Comment: 16 pages. v2) estimates improved, conclusions unchange

Collider Signature of Bulk Neutrinos in Large Extra Dimensions

We consider the collider signature of right-handed neutrinos propagating in $\delta$ (large) extra dimensions, and interacting with Standard Model fields only through a Yukawa coupling to the left-handed neutrino and the Higgs boson. These theories are attractive as they can explain the smallness of the neutrino mass, as has already been shown. We show that if $\delta$ is bigger than two, it can result in an enhancement in the production rate of the Higgs boson, decaying either invisibly or to a $b$ anti-$b$ quark pair, associated with an isolated high $p_T$ charged lepton and missing transverse energy at future hadron colliders, such as the LHC. The enhancement is due to the large number of Kaluza-Klein neutrinos produced in the final state. The observation of the signal event would provide an opportunity to distinguish between the normal and inverted neutrino mass hierarchies, and to determine the absolute scale of neutrino masses by measuring the asymmetry of the observed event numbers in the electron and muon channels.Comment: 31 pages, 13 figures. v2: Added discussion on PDF uncertainties, added reference

Viable Supersymmetry and Leptogenesis with Anomaly Mediation

The seesaw mechanism that explains the small neutrino masses comes naturally with supersymmetric (SUSY) grand unification and leptogenesis. However, the framework suffers from the SUSY flavor and CP problems, and has a severe cosmological gravitino problem. We propose anomaly mediation as a simple solution to all these problems, which is viable once supplemented by the D-terms for U(1)_Y and U(1)_{B-L}. Even though the right-handed neutrino mass explicitly breaks U(1)_{B-L} and hence reintroduces the flavor problem, we show that it lacks the logarithmic enhancement and poses no threat to the framework. The thermal leptogenesis is then made easily consistent with the gravitino constraint.Comment: 5 pages, one figure, uses Revtex4; Discussion on the upper bound on the LSP mass added. The version published in PR

Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard Model

We discuss the main features of dilaton interactions for fundamental and effective dilaton fields. In particular, we elaborate on the various ways in which dilatons can couple to the Standard Model and on the role played by the conformal anomaly as a way to characterize their interactions. In the case of a dilaton derived from a metric compactification (graviscalar), we present the structure of the radiative corrections to its decay into two photons, a photon and a $Z$, two $Z$ gauge bosons and two gluons, together with their renormalization properties. We prove that, in the electroweak sector, the renormalization of the theory is guaranteed only if the Higgs is conformally coupled. For such a dilaton, its coupling to the trace anomaly is quite general, and determines, for instance, an enhancement of its decay rates into two photons and two gluons. We then turn our attention to theories containing a non-gravitational (effective) dilaton, which, in our perturbative analysis, manifests as a pseudo-Nambu Goldstone mode of the dilatation current ($J_D$). The infrared coupling of such a state to the two-photons and to the two-gluons sector, and the corresponding anomaly enhancements of its decay rates in these channels, is critically analyzed.Comment: Revised version, 42 pages, 5 figure

Direct CP violation in charm and flavor mixing beyond the SM

We analyze possible interpretations of the recent LHCb evidence for CP violation in D meson decays in terms of physics beyond the Standard Model. On general grounds, models in which the primary source of flavor violation is linked to the breaking of chiral symmetry (left-right flavor mixing) are natural candidates to explain this effect, via enhanced chromomagnetic operators. In the case of supersymmetric models, we identify two motivated scenarios: disoriented A-terms and split families. These structures predict other non-standard signals, such as nuclear EDMs close to their present bounds and, possibly, tiny but visible deviations in K and B physics, or even sizable flavor-violating processes involving the top quark or the stops. Some of these connections, especially the one with nuclear EDMs, hold beyond supersymmetry, as illustrated with the help of prototype non-supersymmetric models.Comment: 30 pages, 6 figure