The holographic composite Higgs

Theories where the Higgs boson is a composite particle elegantly solve the hierarchy problem. This idea has been recently investigated in the framework of 5-dimensional warped models that, according to the AdS/CFT correspondence, have a 4-dimensional holographic interpretation in terms of strongly coupled field theories. We present a minimal model in which the Higgs arises as a pseudo-Goldstone boson and the electroweak symmetry is dynamically broken. This model can successfully solve the flavor problem and pass all the electroweak precision tests. To cite this article: R. Contino, A. Pomarol, C. R. Physique 8 (2007).     

Goldstone excitation and symmetry-breaking mechanism in superfluid-He4

Summary The form of Goldstone excitation in superfluid He⁴ is envisaged by the formalism of scaling transformation. This is achieved within the framework of symmetry-breaking mechanism which is akin to that of the relativistic quantum field theory. During the editorial procedure we came to know that this author deceased     

Higgs boson production at CLIC in SUSY models with hierarchy of the vacuum expectation values

Many theoretical schemes predict the existence of unconventional quarks and leptons not fitting the standard pattern of fermion families. We consider two possible kinds of non-standard fermions, mirror fermions and exceptional fermions. Mirror fermions arise in a variety of models ranging from family unification to extended supersymmetry and Kaluza-Klein theories; exceptional fermions come along with the groupE ₆ which is believed to be the low energy gauge symmetry of the superstring theory. We discuss some physical properties of these non-standard particles relevant for the LEP     

Decays of the Weinberg-Salam Higgs particle in models with two Higgs doublets

In a class of extended Higgs structures containing two Higgs doublets, the decays of the Weinberg-Salam Higgs particle might be significantly different from those in the standard model because it has large branching ratios to decay into light Higgs bosons. We discuss the decays of the Weinberg-Salam Higgs particle with mass range from 7 GeV up to 1 TeV.     

New spectra in the HEIDI Higgs models

We study the so-called HEIDI models, which are renormalizable extensions of the standard model with a higher-dimensional scalar singlet field. As an additional parameter we consider a higher-dimensional mixing mass parameter. This leads to enriched possibilities compared to a previous study. We find effective spectral densities of the Higgs propagator, consisting of one, two or no particle peaks, together with a continuum. We compare with the LEP-2 data and determine for which range of the model parameters the data can be described. Assuming two peaks to be present we find for the new mass scale ν≈56±12 GeV, largely independent of the dimension. In the limiting case of d→6 and two peaks we find a higher-dimensional coupling constant α₆=0.70±0.18, indicative of strong interactions among the higher-dimensional fields. This Higgs might escape discovery at the LHC. That would provide a strong physics case for building a new lepton collider.     

Higgs bosons in the simplest SUSY models

Nowadays, in the MSSM, the moderate values of tan β are almost excluded by the LEP II lower bound on the mass of the lightest Higgs boson. In the next-to-minimal supersymmetric standard model (NMSSM), the theoretical upper bound on it increases and reaches a maximal value in the limit of strong Yukawa coupling, where all solutions to renormalization-group equations are concentrated near the quasifixed point. For a calculation of the Higgs boson spectrum, the perturbation-theory method can be applied. We investigate the particle spectrum within the modified NMSSM, which leads to the self-consistent solution in the limit of strong Yukawa coupling. This model allows one to get m _h～125 GeV at tan β≥1.9. In the model under investigation, the mass of the lightest Higgs boson does not exceed 130.5±3.5 GeV. The upper bound on the mass of the lightest CP-even Higgs boson in more complicated supersymmetric models is also discussed.     

Distinguish models mimicking the SM Higgs

The new particle around 125 GeV observed at the LHC is almost consistent with the standard model Higgs boson, except that the diphoton decay mode may be excessive. We summarize a number of possibilities. We propose to use the vector-boson fusion to test the underlying model for electroweak symmetry breaking. Using the well known dijet-tagging technique to single out the vector-boson fusion mechanism, we investigate potential of vector-boson fusion to discriminate a number of models suggested to give an enhanced inclusive diphoton production rate.