Influence of strongly coupled,hidden scalars on Higgs signals

To investigate the possible effects of a light hidden sector on Higgs boson detection, we discuss a model of scalar singlets coupled to the Standard Model. The model effectively makes the Higgs width a free parameter due to additional invisible decay modes. This width can become arbitrarily large. Theoretical and experimental bounds on model parameters are presented. It is shown, how Standard Model predictions change and that in the case of large coupling, Higgs signals will be diluted. We study, to which extent such a strongly coupled, hidden sector can be excluded by present and future Higgs search experiments.     

Dark Supersymmetry

We propose a model of Dark Supersymmetry, where a supersymmetric dark sector is coupled to the classically scale invariant non-supersymmetric Standard Model through the Higgs portal. The dark sector contains a mass scale that is protected against radiative corrections by supersymmetry, and the portal coupling mediates this scale to the Standard Model, resulting in a vacuum expectation value for the Higgs field and the usual electroweak symmetry breaking mechanism. The supersymmetric dark sector contains dark matter candidates, and we show that the observed dark matter abundance is generated for a natural choice of parameters, while avoiding the current experimental bounds on direct detection. Future experiments can probe this scenario if the dark sector mass scale is not too high.     

Particle physics models of inflation and curvaton scenarios

We review the particle theory origin of inflation and curvaton mechanisms for generating large scale structures and the observed temperature anisotropy in the cosmic microwave background (CMB) radiation. Since inflaton or curvaton energy density creates all matter, it is important to understand the process of reheating and preheating into the relevant degrees of freedom required for the success of Big Bang Nucleosynthesis. We discuss two distinct classes of models, one where inflaton and curvaton belong to the hidden sector, which are coupled to the Standard Model gauge sector very weakly. There is another class of models of inflaton and curvaton, which are embedded within Minimal Supersymmetric Standard Model (MSSM) gauge group and beyond, and whose origins lie within gauge invariant combinations of supersymmetric quarks and leptons. Their masses and couplings are all well motivated from low energy physics, therefore such models provide us with a unique opportunity that they can be verified/falsified by the CMB data and also by the future collider and non-collider based experiments. We then briefly discuss the stringy origin of inflation, alternative cosmological scenarios, and bouncing universes.     

Thermally favourable gauge mediation

We discuss the thermal evolution of the spurion and messenger fields of ordinary gauge mediation models taking into account the Standard Model degrees of freedom. It is shown that for thermalized messengers the metastable susy breaking vacuum becomes thermally selected provided that the susy breaking sector is sufficiently weakly coupled to messengers or to any other observable field.     

First Principles Calculation of the Baryon Asymmetry of the Universe: Generalities and Application

We present a formalism that allows the computation of the lepton asymmetry of the universe from first principles of statistical physics and quantum field theory (this lepton asymmetry is then converted to a baryon asymmetry via sphaleron processes). This formalism includes a thermal bath of Standard Model particles (active neutrinos) coupled to a new sector that is out-of-equilibrium (sterile neutrinos). The key point that allows a first principles computation is that the number of sterile neutrinos produced during the relevant cosmological period remains small (we assume zero sterile neutrinos initially). In such a case, it is possible to expand the formal solution of Liouville's equation perturbatively and obtain a master formula for the lepton asymmetry expressed in terms of non-equilibrium Wightman functions. The master formula neatly separates CP-violating contributions from finite temperature correlation functions and satisfies all three Sakharov conditions. These correlation functions can then be evaluated perturbatively; the validity of the perturbative expansion depends on the parameters of the model considered. Here we choose the νMSM (i.e. a minimal extension of the Standard Model that includes three generations of sterile neutrinos with masses of the order of the electroweak scale) to illustrate the use of the formalism, but it could in principle be applied to other models.     

On the decay of unparticles

We show that when the unparticle sector is coupled to the Standard Model, unparticle excitations can decay to Standard Model particles. This radically modifies the signals of unparticle production. We present a method for the calculation of the decay lifetimes of unparticles. In a particular model, we show that depending on their lifetime, unparticles can manifest themselves through monojets, delayed events or prompt decays.     

On axionic dark matter in Type IIA string theory

We investigate viable scenarios with various axions in the context of supersymmetric field theory and in globally consistent D‐brane models. The Peccei‐Quinn symmetry is associated with an anomalous U(1) symmetry, which acquires mass at the string scale but remains as a perturbative global symmetry at low energies. The origin of the scalar Higgs‐axion potential from F‐, D‐ and soft breaking terms is derived, and two Standard Model examples of global intersecting D6‐brane models in Type II orientifolds are presented, which differ in the realisation of the Higgs sector and in the hidden sector, the latter of which is of particluar importance for the soft supersymmetry breaking terms.     

Towards gauge unified,supersymmetric hidden strong dynamics

We consider a class of models with extra complex scalars that are charged under both the Standard Model and a hidden strongly coupled S U(N)h gauge sector and discuss the seenarios in which the new scalars are identified as the messenger fields that mediate the spontaneously broken supersymmetries from the hidden sector to the visible sector.The new scalars are embedded into 5-plets and 10-plets of an S(/(5)v gauge group that potentially unifies the Standard Model gauge groups.The Higgs bosons remain as elementary particles.In the supersymmetrized version of this class of models,vector-like fermions whose left-handed components are superpartners of the new scalars are introduced.Owing to the hidden strong force,the new low-energy scalars hadronize before decaying and thus evade the common direct searches of the supersymmetric squarks.This can be seen as a gauge mediation seenario with the scalar messenger fields forming low-energy bound states.We also discuss the possibility that in the tower of bound states formed under hidden strong dynamics(of at least the TeV scale),there exist a dark matter candidate and the collider signatures(e.g.diphoton,diboson,or dijet)of models that may show up in the near future.     

The spherically symmetric Standard Model with gravity

Spherical reduction of generic four-dimensional theories is revisited. Three different notions of “spherical symmetry” are defined. The following sectors are investigated: Einstein-Cartan theory, spinors, (non-)abelian gauge fields and scalar fields. In each sector a different formalism seems to be most convenient: the Cartan formulation of gravity works best in the purely gravitational sector, the Einstein formulation is convenient for the Yang-Mills sector and for reducing scalar fields, and the Newman-Penrose formalism seems to be the most transparent one in the fermionic sector. Combining them the spherically reduced Standard Model of particle physics together with the usually omitted gravity part can be presented as a two-dimensional (dilaton gravity) theory.     

Comments on unparticles

We comment on several points concerning unparticles which have been overlooked in the literature. One regards Mack's unitarity constraint lower bounds on CFT operator dimensions, e.g., dV?3$d_V?3$ for primary, gauge invariant, vector unparticle operators. We correct the results in the literature to account for this, and also for a needed correction in the form of the propagator for vector and tensor unparticles. We show that the unitarity constraints can be directly related to unitarity requirements on scattering amplitudes of particles, e.g., those of the Standard Model, coupled to the CFT operators. We also stress the existence of explicit Standard Model contact terms, which are generically induced by the coupling to the CFT (or any other hidden sector), and are subject to LEP bounds. Barring an unknown mechanism to tune away these contact interactions, they can swamp interference effects generated by the CFT. We illustrate these points in the context of a weakly coupled CFT example. A significant amount of the unparticle literature should be reconsidered or revised in light of the observations in this note.     

Properties of the Higgs particle in a model involving a single unified fermion generation

The properties of the Higgs boson are studied within a model where three generations of Standard Model fermions emerge from one generation in a theory featuring two extra spatial dimensions. It is shown that, despite a nontrivial external field forming a brane, the interactions of the Higgs particle in the effective four-dimensional theory are virtually identical to the interactions of this particle in the Standard Model. Arguments in favor of the statement that the Higgs boson must be rather light in the model being considered are also presented.     

One-loop wave-function renormalization corrections in the scalar sector of the Minimal Supersymmetric Standard Model

One-loop field-renormalization corrections for the two-doublet Higgs potential of the Minimal Supersymmetric Standard Model are obtained within the formalism of finite-temperature quantum field theory. The inclusion of these corrections is necessary for describing the evolution of potential parameters with temperature and affects the electroweak phase transition. In the limiting case where all mass parameters of the squark sector are degenerate and where the temperature is zero, the potential parameters coincide with the results obtained previously.     

Exploring the Higgs portal

We study the Higgs portal from the Standard-Model to a hidden sector and examine which elements of the extended theory can be discovered and explored at the LHC. Our model includes two Higgs bosons covering parameter regions where the LHC will be sensitive to two, one or none of the particles at typical discovery luminosities for Standard Model Higgs production.     

SEWDarkM

A number of observed phenomena in high energy physics and cosmology lack their resolution within the Standard Model of particle physics. These puzzles include neutrino oscillations, baryon asymmetry of the Universe, existence of Dark Matter and inflation. We discuss the suggestion, based on the νMSM (an extension of the Standard Model by three light singlet fermions) that all these problems can be solved by new physics which exists only below the electroweak scale. We describe the formalism which allows to compute from first principles of quantum field theory and statistical physics the abundance of dark matter in this theory. Predictions of the νMSM are compared with results of different cosmological and astrophysical observations.     

Lorentz violation from the Higgs portal

We study bounds and signatures of models where the Higgs doublet has an inhomogeneous mass or vacuum expectation value, being coupled to a hidden sector that breaks Lorentz invariance. This physics is best described by a low-energy effective Lagrangian in which the Higgs speed-of-light is smaller than c; such effect is naturally small because it is suppressed by four powers of the inhomogeneity scale. The Lorentz violation in the Higgs sector is communicated at tree level to fermions (via Yukawa interactions) and to massive gauge bosons, although the most important effect comes from one-loop diagrams for photons and from two-loop diagrams for fermions. We calculate these effects by deriving the renormalization-group equations for the speed-of-light of the Standard Model particles. An interesting feature is that the strong coupling dynamically makes the speed-of-light equal for all colored particles.     

Manifestly Covariant Quantum Theory with Invariant Evolution Parameter in Relativistic Dynamics

Manifestly covariant quantum theory with invariant evolution parameter is a parametrized relativistic dynamical theory. The study of parameterized relativistic dynamics (PRD) helps us understand the consequences of changing key assumptions of quantum field theory (QFT). QFT has been very successful at explaining physical observations and is the basis of the conventional paradigm, which includes the Standard Model of electroweak and strong interactions. Despite its record of success, some phenomena are anomalies that may require a modification of the Standard Model. The anomalies include neutrino oscillations, non-locality, and gravity.     

: a rising star on the stage of flavour physics

Motivated by the new experimental information reported by the BNL-E787 Collaboration, we analyse the present impact and the future prospects opened by the measurement of . Although still affected by a large error, the BNL-E787 result favours values of substantially larger than what expected within the Standard Model. As a result, this data already provide non-trivial constraints on the unitarity triangle, when interpreted within the Standard Model framework. We stress the importance of the clean relation between , sin2β and ΔM_Bd/ΔM_Bs that in the next few years could provide one of the deepest probes of the Standard Model in the sector of quark-flavour dynamics. A speculative discussion about possible non-standard interpretations of a large is also presented. Two main scenarios naturally emerge: those with direct new-physics contributions to the amplitude and those with direct new-physics effects only in B_d– mixing. Realistic models originating these two scenarios and possible future strategies to clearly identify them are briefly discussed.     

Charged nontopological soliton of the <Emphasis Type="Italic">SU</Emphasis>(2) × <Emphasis Type="Italic">U</Emphasis>(1) gauge model

The SU(2) × U(1) gauge model that is the bosonic sector of the Standard Model of electroweak interactions is considered. The existence of electrically charged nontopological solitons is shown to be possible in this model. Some properties of a charged nontopological soliton are investigated. Asymptotic expressions are derived for the soliton radius, energy, and phase frequency in the thin-wall regime by the method of trial functions. Numerical solutions of the model field equations corresponding to electrically charged non-topological solitions have been obtained. The dependences of the soliton energy and charge on phase frequency are given for several model parameters. It follows from the data obtained that there exists a domain of parameters in which a charged nontopological soliton is stable to the transition to a plane-wave field configuration.     

Anomaly driven signatures of new invisible physics at the Large Hadron Collider

Many extensions of the Standard Model (SM) predict new neutral vector bosons at energies accessible by the Large Hadron Collider (LHC). We study an extension of the SM with new chiral fermions subject to non-trivial anomaly cancellations. If the new fermions have SM charges, but are too heavy to be created at LHC, and the SM fermions are not charged under the extra gauge field, one would expect that this new sector remains completely invisible at LHC. We show, however, that a non-trivial anomaly cancellation between the new heavy fermions may give rise to observable effects in the gauge boson sector that can be seen at the LHC and distinguished from backgrounds.     

Conformal symmetry and the Standard Model

We re-examine the question of radiative symmetry breaking in the Standard Model in the presence of right-chiral neutrinos and a minimally enlarged scalar sector. We demonstrate that, with these extra ingredients, the hypothesis of classically unbroken conformal symmetry, besides naturally introducing and stabilizing a hierarchy, is compatible with all available data; in particular, there exists a set of parameters for which the model may remain viable even up to the Planck scale. The decay modes of the extra scalar field provide a unique signature of this model which can be tested at LHC.