Radiatively generated maximal mixing scenario for the Higgs boson mass and the least fine-tuned minimal supersymmetric standard model

We argue that given the experimental constraints on the Higgs boson mass the least fine-tuned parameter space of the minimal supersymmetric standard model is with negative top-squark masses squared at the grand unification scale. While the top-squark mass squared is typically driven to positive values at the weak scale, the contribution to the Higgs boson mass squared parameter from the running can be arbitrarily small, which reduces the fine-tuning of electroweak symmetry breaking. At the same time the top-squark mixing is necessarily enhanced and the maximal mixing scenario for the Higgs boson mass can be generated radiatively even when starting with negligible mixing at the unification scale. This highly alleviates constraints on possible models for supersymmetry breaking in which fine-tuning is absent.     

Type 1 2HDM as Effective Theory of Supersymmetry

It is generally believed that the low energy effective theory of the minimal supersymmetric standard model is the type 2 two Higgs doublet model. We will show that the type 1 two Higgs doublet model can also be as the effective of supersymmetry in a specific case with high scale supersymmetry breaking and gauge mediation. If the other electroweak doublet obtain the vacuum expectation value after the electroweak symmetry breaking, the Higgs spectrum is quite different. A remarkable feature is that the physical Higgs boson mass can be 125 GeV unlike in the ordinary models with high scale supersymmetry in which the Higgs mass is generally around 140 GeV.     

Type 1 2HDM as Effective Theory of Supersymmetry

It is generally believed that the low energy effective theory of the minimal supersymmetric standard model is the type 2 two Higgs doublet model.We will show that the type 1 two Higgs doublet model can also be as the effective of supersymmetry in a specific case with high scale supersymmetry breaking and gauge mediation.If the other electroweak doublet obtain the vacuum expectation value after the electroweak symmetry breaking,the Higgs spectrum is quite different.A remarkable feature is that the physical Higgs boson mass can be 125 GeV unlike in the ordinary models with high scale supersymmetry in which the Higgs mass is generally around 140 GeV.     

Superconformal technicolor

In supersymmetric theories with a strong conformal sector, soft supersymmetry breaking at the TeV scale naturally gives rise to confinement and chiral symmetry breaking at the same scale. We consider two such scenarios, one where the strong dynamics induces vacuum expectation values for elementary Higgs fields, and another where the strong dynamics is solely responsible for electroweak symmetry breaking. In both cases, the mass of the Higgs boson can exceed the LEP bound without tuning, solving the supersymmetry naturalness problem. A good precision electroweak fit can be obtained, and quark and lepton masses are generated without flavor-changing neutral currents. In addition to standard supersymmetry signals, these models predict production of multiple heavy standard model particles (t, W, Z, and b) from decays of resonances in the strong sector.     

Superconductivity in Supersymmetric Theories

The study of superconductivity has been undertaken through the breaking of supersymmetric gauge theories which automatically incorporate the condensation of monopoles and dyons leading to confining and superconducting phases. Constructing the effective Lagrangian near a singularity in moduli space for N=2 supersymmetric theory with SU(2) gauge group, it has been shown that when a mass term is added to this Lagrangian, the N=2 Supersymmetry is reduced to N=1 supersymmetry yielding the dyonic condensation which leads to confinement and superconductivity as the consequence of generalized Meissner effect. In the Coulomb phase of N=2 SU(3) Yang–Mills theory the gauge symmetry has been broken down to SU(2)×U(l) and it has been shown that on perturbing it by suitable tree-level superpotential this supersymmetry theory breaks to N=1 SU(2) Yang-Mills theory described by Higgs field in confining phase incorporating superconductivity.     

Double protection of the Higgs potential in a supersymmetric little Higgs model

A mechanism of double protection of the Higgs potential, by supersymmetry and by a global symmetry, is investigated in a class of supersymmetric models with the SU(3)cxSU(3)wxU(1)x gauge symmetry. The electroweak symmetry can be then broken with no fine-tuning at all.     

Nonlinear local supersymmetric SU(5)-model

We construct a realistic nonlinear supersymmetric SU(5) model without superpartner particles in curved space and investigate the Higgs sector in the limit of flat space. We need at least an adjoint-, a quintuplet- and an antiquintuplet-Higgs multiplet. In order to obtain a realistic breakdown of SU(5) to SU(3) × U(1) at tree level we have to modify the vacuum structure of the adjoint representation in comparison to other SU(5)-models. This model requires an “elegant” fine-tuning. We determine the mass spectrum of the electroweak Higgs sector.     

Exothermic Transition to a Future Susy Universe

The Higgs sector of the MSSM may be extended to solve the μ problem by the addition of a gauge singlet scalar field. We consider an extended Higgs model. For simplicity we consider the case where all the fields in the scalar sector are real. We analyze the vacuum structure of the model. We address the question of an exothermic phase transition from a broken susy phase with electroweak symmetry breaking (our current universe) to an exact susy phase with electroweak symmetry breaking (future susy universe).     

SU(2)×SU(2) Electroweak Theory I: The B3 Field on the Physical Vacuum

Nonlinear optics confronts the U(1) theory of electrodynamics with the dilemma of the existence of nonlinear fields. The U(1) group is completely linear and Abelian and causes consideration of an SU(2) theory of electrodynamics. An SU(2) theory of electrodynamics, with a B ³ magnetic field, means that physics is forced to consider an SU(2) × SU(2) electroweak theory. It is then demonstrated that the B ³ field exists on the physical vacuum defined by the Higgs symmetry breaking of this extended electroweak theory.     

Origin and phenomenology of weak-doublet spin-1 bosons

We study phenomenological consequences of the Standard Model extension by the new spin-1 fields with the internal quantum numbers of the electroweak Higgs doublets. We show, that there are at least three different classes of theories, all motivated by the hierarchy problem, which predict appearance of such vector weak-doublets not far from the weak scale. The common feature for all the models is the existence of an SUW(3) gauge extension of the weak SUW(2) group, which is broken down to the latter at some energy scale around TeV. The Higgs doublet then emerges as either a pseudo-Nambu-Goldstone boson of a global remnant of SUW(3), or as a symmetry partner of the true eaten-up Goldstone boson. In the third class, the Higgs is a scalar component of a high-dimensional SUW(3) gauge field. The common phenomenological feature of these theories is the existence of the electroweak doublet vectors (Z^?,W^?), which in contrast to well-known Z^′ and W^′ bosons posses only anomalous (magnetic moment type) couplings with ordinary light fermions. This fact leads to some unique signatures for their detection at the hadron colliders.     

Reduction of the finite grand unification theory to the minimal supersymmetric standard model

The recently proposed mechanism for reducing the finite SU(5) grand unification theory (GUT) to the minimal supersymmetric standard model (MSSM) is reanalyzed and simplified. For the scalar SU(2)×U(1) invariant Higgs doublet potential that results from SU(5) symmetry breaking to have no dangerous directions, a restriction on the parameters of the unified theory should be imposed. At the same time, this restriction guarantees that the scalar Higgs doublet potential has a minimum at zero at the GUT scale, and the low-energy theory appears to be exactly the MSSM. Zh. éksp. Teor. Fiz. 111, 787–795 (March 1997) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Discrete symmetry and GUT breaking

We study the supersymmetric GUT models in which the supersymmetry and GUT gauge symmetry can be broken by a discrete symmetry. First, with the ansatz that there exist discrete symmetries in the branes' neighborhoods, we discuss the general reflection symmetries and GUT breaking on and . In those models, the extra dimensions can be large and the KK states can be set arbitrarily heavy. Second, considering that the extra space manifold is the annulus or the disc , we can define any symmetry and break any 6-dimensional N=2 supersymmetric SU(M) models down to the 4-dimensional N=1 supersymmetric models for the zero modes. In particular, there might exist the interesting scenario on where just a few KK states are light, while the others are relatively heavy. Third, we discuss the complete global discrete symmetries on and study the GUT breaking. Received: 12 February 2002 / Published online: 14 June 2002     

Effective two Higgs doublets in nonminimal supersymmetric models

The Higgs sectors of supersymmetric extensions of the Standard Model have two doublets in the minimal version (MSSM), and two doublets plus a singlet in two others: with (UMSSM) and without (NMSSM) an extra U(1)′. A very concise comparison of these three models is possible if we assume that the singlet has a somewhat larger breaking scale compared to the electroweak scale. In that case, the UMSSM and the NMSSM become effectively two-Higgs-doublet models (THDM), like the MSSM. In this approach the well-known upper mass bounds on the lightest CP-even neutral Higgs boson can be derived in a very simple and transparent way.     

Can supersymmetry breaking lead to electroweak symmetry breaking via formation of scalar bound states?

The recent discovery of the putative 125 GeV Higgs boson has motivated a number of attempts to reconcile its relatively large mass with the predictions of the minimal supersymmetric standard model (MSSM). Some approaches invoked large trilinear supersymmetry breaking terms _At$A_t$ between stops and one of the elementary Higgs fields. We consider the possibility that electroweak symmetry breaking may be triggered by supersymmetry breaking with a large _At$A_t$, large enough to generate a composite field with the same quantum numbers as the Higgs boson and with a non-vanishing vacuum expectation value. In the resulting vacuum, the usual relation between the gauge couplings and the Higgs self-coupling does not apply, and there is no reason to expect the same upper bound on the mass of the lightest Higgs boson. In a simple model where the bound state is assumed to have no mixing with the other fields, we calculate the critical coupling _At$A_t$ necessary for symmetry breaking using the lowest-order Bethe–Salpeter (BS) equation. Study of the BS equation is complicated by the structure of its lowest-order kernel, which is a crossed box graph, but we find an accurate approximation to its solution. In a realistic model, the mixing of the bound state with the fundamental Higgs boson creates a symmetry-breaking seesaw. We outline the steps toward a realistic model.     

New physics contribution to neutral trilinear gauge boson couplings

We study the one-loop new physics effects to the CP even triple neutral gauge boson vertices γ ^⋆ γ Z, γ ^⋆ Z Z, Z ^⋆ Z γ and Z ^⋆ ZZ in the context of Little Higgs models. We compute the contribution of the additional fermions in Little Higgs models in the framework of direct product groups where [SU(2)×U(1)]² gauge symmetry is embedded in SU(5) global symmetry and also in the framework of the simple group where SU(N)×U(1) gauge symmetry breaks down to SU(2) _L ×U(1). We calculate the contribution of the fermions to these couplings when T parity is invoked. In addition, we re-examine the MSSM contribution at the chosen point of SPS1a′ and compare with the SM and Little Higgs models.     

First-order electroweak phase transition powered by additional F-term loop effects in an extended supersymmetric Higgs sector

We investigate the one-loop effect of new charged scalar bosons on the Higgs potential at finite temperatures in the supersymmetric standard model with four Higgs doublet chiral superfields as well as a pair of charged singlet chiral superfields. In this model, the mass of the lightest Higgs boson h is determined only by the D-term in the Higgs potential at the tree-level, while the triple Higgs boson coupling for hhh can receive a significant radiative correction due to nondecoupling one-loop contributions of the additional charged scalar bosons. We find that the same nondecoupling mechanism can also contribute to realize stronger first order electroweak phase transition than that in the minimal supersymmetric standard model, which is definitely required for a successful scenario of electroweak baryogenesis. Therefore, this model can be a new candidate for a model in which the baryon asymmetry of the Universe is explained at the electroweak scale.     

Electroweak breaking and supersymmetry breaking

We discuss the clash between the absence of fine tuning in the Higgs potential and a sufficient suppression of flavour changing neutral current transitions in supersymmetric extensions of the standard model. It is pointed out that horizontalU(1) symmetry combined with theD-term supersymmetry breaking provides a realistic framework for solving both problems.     

The Impact of the LHC on Cosmology

The last 2 years has seen an immense amount of activity and results from the Large Hadron Collider (LHC). Most notable is the discovery of a new particle which may very well be the long sought Higgs boson associated with electroweak symmetry breaking. There have also been many (up to now) unsuccessful searches for new particles associated with supersymmetry. One of the most attractive candidates for dark matter is the lightest supersymmetric particle (LSP). The recent results from the LHC have had a dramatic impact on our expectations for the properties of the LSP. These results can be used to revise expectations for both direct and indirect detection of dark matter.     

High transverse momentum physics at the large hadron collider

This note summarizes many detailed physics studies done by the ATLAS and CMS Collaborations for the LHC, concentrating on processes involving the production of high mass states. These studies show that the LHC should be able to elucidate the mechanism of electroweak symmetry breaking and to study a variety of other topics related to physics at the TeV scale. In particular, a Higgs boson with couplings given by the Standard Model is observable in several channels over the full range of allowed masses. Its mass and some of its couplings will be determined. If supersymmetry is relevant to electroweak interactions, it will be discovered and the properties of many supersymmetric particles elucidated. Other new physics, such as the existence of massive gauge bosons and extra dimensions can be searched for extending existing limits by an order of magnitude or more.     

Supersymmetric SU C (4) × SU L (2) × SU R (2) and spontaneous breakdown of symmetries

A supersymmetric version of the left right symmetric partial unification group SU _C (4) × SU _L (2) × SU _R (2) is presented. The spontaneous breakdown of gauge symmetry in a favourable chain of descent has been studied in detail. The mass spectra have been calculated. The method of O’Raifeartaigh has been used to break supersymmetry. The lifting of degeneracy of mass levels between physical multiplets has been shown to occur due to radiative corrections.