We analyze the spectrum and properties of a highly deconstructed Higgsless model with only three sites. Such a model contains sufficient complexity to incorporate interesting physics issues related to fermion masses and electroweak observables, yet remains simple enough that it could be encoded in a Matrix Element Generator program for use with Monte Carlo simulations. The gauge sector of this model is equivalent to that of the Breaking Electroweak Symmetry Strongly (BESS) model; the new physics of interest here lies in the fermion sector. We analyze the form of the fermion Yukawa couplings required to produce the ideal fermion delocalization that causes tree-level precision electroweak corrections to vanish. We discuss the size of one-loop corrections to b ! s, the weak-isospin violating parameter T and the decay Z ! b b. We find that the new fermiophobic vector states (the analogs of the gauge-boson KaluzaKlein modes in a continuum model) can be reasonably light, with a mass as low as 380 GeV, while the extra (approximately vectorial) quark and lepton states (the analogs of the fermion Kaluza-Klein modes) must be heavier than 1.8 TeV.

We provide a pedagogical introduction to extensions of the Standard Model in which the Higgs is composite. These extensions are known as models of dynamical electroweak symmetry breaking or, in brief, Technicolor. Material covered includes: motivations for Technicolor, the construction of underlying gauge theories leading to minimal models of Technicolor, the comparison with electroweak precision data, the low energy effective theory, the spectrum of the states common to most of the Technicolor models, the decays of the composite particles and the experimental signals at the Large Hadron Collider. The level of the presentation is aimed at readers familiar with the Standard Model but who have little or no prior exposure to Technicolor. Several extensions of the Standard Model featuring a composite Higgs can be reduced to the effective Lagrangian introduced in the text.We establish the relevant experimental benchmarks for Vanilla, Running, Walking, and Custodial Technicolor, and a natural fourth family of leptons, by laying out the framework to discover these models at the Large Hadron Collider.

We revisit an extension of the MSSM by adding a hypercharge-neutral, SU (2)-triplet chiral superfield. Similar to the NMSSM, the triplet gives an additional contribution to the quartic coupling in the Higgs potential, and the mass of the lightest CP -even Higgs boson can be greater than MZ at tree-level. In addition to discussing the perturbativity, fine-tuning, and decoupling issues of this model, we compute the dominant 1-loop corrections to the mass of the lightest CP -even Higgs boson from the triplet sector. When the Higgs-Higgs-Triplet coupling in the superpotential is comparable to the top Yukawa coupling, we find that the Higgs mass can be as heavy as 140 GeV even without the traditional contributions from the top-s-top sector, and at the same time consistent with the precision electroweak constraints. At the expense of having Landau poles before the GUT scale, this opens up a previously forbidden region in the MSSM parameter space where both s-tops are light. In addition to having relatively small fine-tuning (about one part in 30), this leads to a gluo-philic Higgs boson whose production via gluon-gluon fusion at the LHC can be twice as large as the SM In this paper, we extend the MSSM with a hypercharge-neutral, SU (2)-triplet chiral superfield T and name the model triplet-extended supersymmetric standard model (TESSM). Extensions of this type have been studied extensively by Espinosa and Quiros [29][30], Felix-Beltran [31], Setzer and Spinner [32], and Diaz-Cruz et al. [33]. While this model does not solve the µ-problem, it is an interesting alternative to the NMSSM, as an economical extension of the MSSM, because it can also achieve a mass of the lightest CP -even Higgs boson that is larger than M Z at tree level. Furthermore, compared to the MSSM and the NMSSM, we expect there to be more radiative corrections to the mass of the lightest CP -even Higgs boson due to the additional states in the triplet. To the extent that these triplet-induced radiative corrections are significant, we may further alleviate the little hierarchy problem.Unfortunately, in both the NMSSM and the TESSM, the respective singlet-induced and triplet-induced radiative corrections are typically small when we demand perturbativity at the scale of grand unified theory (GUT) near 10 16 GeV. This is because perturbativity at the GUT scale imposes the bound λ < ∼ 0.7 at the weak scale, where λ is respectively the Higgs-singlet-Higgs and the Higgs-triplet-Higgs coupling in the superpotential of the NMSSM and TESSM. In both models, while the tree-level mass of the lightest CP -even Higgs boson can be as large as 100 GeV, the O(λ 4 ) radiative corrections are not large enough to lift the Higgs mass over the LEP bounds. On the other hand, in the TESSM, when we have λ ∼ 0.9 (so that λ is comparable with the top Yukawa coupling)at the weak scale, we find the tree-level mass of the lightest CP -even Higgs boson to be close to the LEP bound and the O(λ 4 ) radiative corrections alone can easily lift the Higgs mass over the LEP bound even wit...

We scrutinise the evidences recently reported by the ATLAS and CMS collaborations for compatible 750 GeV resonances which appear in the di-photon channels of the two experiments in both the 8 TeV and 13 TeV datasets. Similar resonances in di-boson, di-lepton, di-jet and tt final states are instead not detected. After discussing the properties and the compatibility of the reported signals, we study the implications on the physics beyond the Standard Model with particular emphasis on possible scalar extensions of the theory such as singlet extensions and the two Higgs doublet models. We also analyse the significance of the new experimental indications within the frameworks of the minimal supersymmetric standard model and of technicolour models. Our results show that a simple effective singlet extension of the SM achieves phenomenological viability with a minimal number of free parameters. The minimal supersymmetric model and the two Higgs doublet model, on the other hand, cannot explain the 750 GeV di-photon excess. Compatibility with the observed signal requires the extension of the particle content of these models, for instance by heavy vector quarks in the case of the two Higgs doublet model.

The relaxion scenario presents an intriguing extension of the standard model in which the particle introduced to solve to the strong CP problem, the axion, also achieves the dynamical relaxation of the Higgs boson mass term. In this work we complete this framework by proposing a scenario of inflationary cosmology that is consistent with all the observational constraints: the relaxion hybrid inflation with an asymmetric waterfall. In our scheme, the vacuum energy of the inflaton drives inflation in a natural way while the relaxion slow-rolls. The constraints on the present inflationary observables are then matched through a subsequent inflationary epoch driven by the inflaton. We quantify the amount of fine-tuning of the proposed inflation scenario, concluding that the inflaton sector severely decreases the naturalness of the theory.