Composite Higgs Boson Research Articles

Top-color dynamics and the effective gluon-gluon-Higgs operator

We discuss the production of the composite Higgs boson in topcolor models via the gluon fusion process. We consider the contribution of color-octet massive gauge bosons (colorons) strongly interacting with the top quark, in addition to nonstandard contributions of the top-Yukawa coupling and heavy colored fermions other than the top quark. In order to estimate the contribution of colorons, we derive the low-energy effective theory by eliminating colorons by using the equation of motion for colorons. We replace the composite operator (\bar{q}_L t_R)(\bar{t}_R q_L) in the effective theory by the composite Higgs operator. We then obtain the effective gluon-gluon-Higgs (ggH-) operator induced by colorons and find that its coefficient (A_{col}) is proportional to m_{dyn}^2/M^2, where M and m_{dyn} denote the coloron mass and the mass dynamically generated by colorons, respectively. The contribution of colorons A_{col} becomes comparable to the top-loop effect A_{top} for M=O(1TeV) and m_{dyn}=O(0.6TeV). Such a large dynamical mass can be realized in top-seesaw (TSS) models consistently with the experimental value of the top quark mass (m_t^{exp}), while the dynamical mass itself is adjusted to m_t^{exp} in topcolor assisted technicolor models (TC2). We find that the coloron contribution A_{col} can be sizable in a certain class of TSS models: the contribution of colorons (the top-loop) is dominant in the real (imaginary) part of the H->gg amplitude for the Higgs boson mass m_H of the order of 1 TeV. On the other hand, enhancement of the top-Yukawa coupling becomes important in TC2. We can observe signatures of the Higgs boson in TC2 with m_H \sim 200 GeV even at the Tevatron Run II as well as at the LHC. We estimate S/\sqrt{B}=3-6 for an integrated luminosity of 2 fb^{-1} and m_H=190 GeV at the Tevatron Run II.

Case study in dimensional deconstruction

We test Arkani-Hamed et al.'s dimensional deconstruction on a model that is predicted to have a naturally light composite Higgs boson, i.e., one whose mass M is much less than its binding scale \Lambda, and whose quartic coupling \lambda is large, so that its vacuum expectation value v \sim M/\sqrt{\lambda} << \Lambda also. We consider two different underlying dynamics--UV completions--at the scale \Lambda for this model. We find that the expectation from dimensional deconstruction is not realized and that low energy details depend crucially on the UV completion. In one case, M << \Lambda and \lambda << 1, hence, v \sim \Lambda. In the other, \lambda can be large or small, but then so is M, and v is still O(\Lambda).

Top quark seesaw model, vacuum structure, and electroweak precision constraints

We present a complete study of the vacuum structure of top quark seesaw models of the electroweak symmetry breaking, including bottom quark mass generation. Such models emerge naturally from bosonic extra dimensions. We perform a systematic gap equation analysis and develop an improved broken phase formulation for including exact seesaw mixings. The composite Higgs boson spectrum is studied in the large-${N}_{c}$ fermion-bubble approximation and an improved renormalization group approach. The theoretically allowed parameter space is restrictive, leading to well-defined predictions. We further analyze the electroweak precision constraints. Generically, a heavy composite Higgs boson with a mass of $\ensuremath{\sim}1 \mathrm{TeV}$ is predicted, yet fully compatible with the precision data.

Top Quark, Heavy Fermions and the Composite Higgs Boson**The project supported in part by National Natural Science Foundation of China under Grant No. 19775005

We study the properties of heavy fermions in the vector-like representation of the electroweak gauge group with Yukawa couplings to the standard model Higgs boson. Applying the renormalization group analysis, we discuss the effects of heavy fermions to the vacuum stability bound and the triviality bound on the mass of the Higgs boson. We also discuss the interesting possibility that the Higgs particle is composed of the top quark and heavy fermions. The bound on the composite Higgs mass is estimated using the method of Bardeen, Hill and Lindner (Phys. Rev. D41 (1990) 1647), .

FERMION-SECTOR FRUSTRATED SU(4) AS A PREONIC PRECURSOR OF THE STANDARD MODEL

We give a model for composite quarks and leptons based on the semisimple gauge group SU(4), with the preons in the 10 representation; this choice of gauge gluon and preon multiplets is motivated by the possibility of embedding them in an N=6 supergravity multiplet, with the preons and antipreons both in the 20 of SU(6). Hypercolor singlets are forbidden in the fermionic sector of this theory; we propose that the SU(4) symmetry spontaneously breaks to SU (3)× U (1), with the binding of triality nonzero preons and gluons into composites, and with the formation of a color singlet condensate that breaks the initial Z12 vacuum symmetry to Z6. The spin ½ fermionic composites have the triality structure of a quark–lepton family, and the initial Z12 symmetry implies that there are six massless families, which mix to give three distinct families below the scale of the condensate. The spin 1 triality zero composites of the color triplet SU(4) gluons, when coupled to the condensate and with the color singlet representation of the 10 acting as a doorway state, lead to weak interactions of the fermionic composites through an SU(2) gauge algebra. The initial Z12 symmetry implies that this SU(2) gauge algebra structure is doubled, which in turn permits the corresponding independent gauge bosons to couple to chiral components of the composite fermions. Since the U(1) couples to the 10 representation as B-L, an effective SU (2)L× SU (2)R × U (1)B-L electroweak theory arises at the condensate scale, with all composites having the correct electric charge structure. Assuming a mechanism for forming composite Higgs bosons, the Z12→ Z6 symmetry breaking chain implies that below the condensate scale there can be two sets of discrete chiral Z6 triplets of Higgs doublets, as required by a phenomenological model for the CKM matrix that we have analyzed in detail elsewhere. A renormalization group analysis of the SU(4) model shows that the conversion by binding of one 10 of SU(4) to 12 triplets of SU(3) can give a very large, calculable hierarchy ratio between the SU(4) and the hadronic mass scales.

RADIATIVE EFFECTS AND ELECTROWEAK SYMMETRY BREAKING IN A SUPERSYMMETRIC PREON MODEL

We construct the low energy effective theory of composite quarks, leptons, and Higgs bosons for a supersymmetric preon model and study the effects of renormalization-group based radiative corrections. The study on the evolution of scalar masses for avoiding color and charge breakings leads us to conclude that Yukawa couplings are bounded from above. The implementation of electroweak symmetry breaking requires that only the purely dynamical symmetry breaking should be needed for the model, but the combined scheme of dynamical and radiative symmetry breaking as well as the purely radiative symmetry breaking scheme be disfavored. Our analysis of [Formula: see text] including radiative effects shows that, should a discrepancy be found between the observed and the theoretical value of [Formula: see text] after experimental determination of supersymmetric particle masses, it would imply that the complete quark–lepton universality in the supersymmetric preon model does not hold either for the Yukawa couplings, or for the condensates, or for both.

Top quark seesaw theory of electroweak symmetry breaking

We study electroweak symmetry breaking involving the seesaw mechanism of quark condensation. These models produce a composite Higgs boson involving the left-handed top quark, yet the top mass arises naturally at the observed scale. We describe a schematic model which illustrates the general dynamical ideas. We also consider a generic low-energy effective theory which includes several composite scalars, and we use the effective potential formalism to compute their spectrum. We develop a more detailed model in which certain features of the schematic model are replaced by additional dynamics.

The Higgs boson mass and Ward-Takahashi identity in gauged Nambu-Jona-Lasinio model

A new formula for the composite Higgs boson mass is given, based on the Ward-Takahashi identity and the Schwinger-Dyson(SD) equation. In this formula the dominant asymptotic solution of the SD equation yields a correct answer, in sharp contrast to the Partially Conserved Dilatation Current(PCDC) approach where the sub- and sub-sub-dominant solutions should be taken into account carefully. In the gauged Nambu-Jona-Lasinio model we find M H≃ 2 M for the composite Higgs boson mass M H and the dynamical mass of the fermion M in the case of the constant gauge coupling(with large cut off), which is consistent with the PCDC approach and the renormalization-group approach. As to the case of the running gauge coupling, we find M H≃2 (A−1)/(2A−1) M (A>1,Λ→∞) , where A≡18 C 2/(11 N c −2 N f ) with C 2 being the quadratic Casimir of the fermion representation. We also discuss a straightforward application of our formula to QCD(without 4-Fermi coupling), which yields M σ∼ 2 M dyn , with M σ and M dyn being the light scalar(“ σ-meson”) mass and mass of the constituent quark, respectively.

Ward identity and dynamical mass generation in Abelian gauge theory

We develop Ward-Takahashi identities to include composite fields and utilize them to study gauge symmetry dynamical breaking in Abelian theory. In terms of the equivalence between elementary field description and the composite field description, we obtain a matching condition. The mechanism of mass generation and the mass spectra are investigated in Cornwall-Norton, Jackiw-Johnson, and Schwinger models. The gauge boson masses are in agreement with previous works; meanwhile the composite Higgs boson and decay constant ${F}_{\ensuremath{\pi}},$ which have not been obtained in previous works and other methods, can be easily obtained. It turns out that this approach can be easily applied to study not only the mass generation of fermion and gauge bosons, but also that of composite fields.

TESTING THE VECTOR BOSON DOMINANCE OF ELECTROWEAK INTERACTIONS VIA $e^ + e^ - \to \bar ff$

Restrictions on the universal four-fermion contact interactions are investigated in the framework of the vector boson dominance (VBD) of electroweak interactions for composite leptons, quarks and Higgs bosons. Manifestations of the VBD via these interactions at the 2 TeV e+e− linear collider are studied. Definite signatures of the VBD are exposed. It is shown that the VBD could be tested at the collider for the unified substructure scale up to O(50 TeV), which lies well in the naturally preferred deca-TeV region.

Self-consistent dynamics of a light composite scalar Higgs boson.

We apply a simple approximate relativistic amplitude-unitarization generalization of nonrelativistic Schr\"odinger-equation dynamics to the scattering of longitudinal mass-degenerate $W$ and $Z$ gauge bosons. The strong energy dependence of our amplitude near the $\mathrm{WW}$ threshold then makes possible a nonperturbative self-consistent nonelementary neutral Higgs scalar bound state ($H$) just below this threshold. We must, however, include a constant term approximating high-energy inelastic effects in addition to $H$ exchange. Everything, including the $H$ mass, can then be determined in terms of the small phenomenological $\mathrm{WWH}$ coupling and $W$ mass, which serves to set the energy scale of the problem; this is the same number of arbitrary parameters as in the underlying electroweak theory. The partial-wave amplitude containing the $H$ is then in approximate agreement at zero energy with the one given by the perturbative crossing-symmetric $H$-pole-only tree-graph amplitude. We find unacceptable zero-energy disagreement, however, if, instead of an inelasticity term, we insert a subtraction constant approximating the effect of short-range high-mass exchanges to obtain our $H$. Similar self-consistent $H$ bound-state solutions can also arise near the $t\overline{t}$ threshold in $t\overline{t}$ scattering with $H$ exchange.

Composite model of Higgs bosons

We assume that the Higgs bosons are composed of a preon ≪a≫ and an antipreon ≪aCP≫. It is then shown that the composite Higgs bosons can give the mass to gauge bosons, quarks and leptons in the framework of the standardSU(2)L×U(1) electroweak model.

Comments on the vacuum stability bounds in the case of composite Higgs bosons

In case of one or two Higgs doublets the requirement of the vacuum stability establishes severe bounds between the heaviest Higgs boson mass and the top-quark mass. We argue that for the composite Higgs boson the standard arguments based on the vacuum stability requirement are not applicable and hence we cannot use the stability bound for the top-quark mass.

Towards the nonsupersymmetric solution of the gauge hierarchy problem

>In the Weinberg-Salam model with a composite Higgs boson for the special case when all Yukawa couplings except the t-quark coupling vanish, there is a hidden UL(1)⊗UR(1) gauge symmetry which protects the smallness of the composite Higgs mass against radiative corrections. For the solution of the gauge hierarchy problem we propose a generalization of the Weinberg-Salam model with hidden abelian gauge symmetry.

FORMATION OF COMPOSITE HIGGS BOSONS FROM QUARK-ANTIQUARKS AT LOWER ENERGY SCALES

We study how the simple predictions of the Nambu-Jona-Lasinio model of composite Higgs bosons are modified when quark interactions more singular than the nonderivative four-quark interaction are added. The t-quark mass is no longer restricted to ≳ 200 GeV, the simple mass relation between the t-quark and the scalar Higgs boson is lost, and the energy scale of the quark couplings can be chosen as low as we wish. Implications in experimental testability of this class of models are briefly discussed.

Composite Higgs bosons in the Nambu-Jona-Lasinio model.

If more than one doublet of composite Higgs bosons is formed with quarks and antiquarks alone in the Nambu-Jona-Lasinio model, their couplings to quarks are subject to interesting constraints. The Higgs doublets orthogonal to the linear combination responsible for mass generation almost decouple with the right-handed $t$ quark, but couple with one or more of the right-handed $u$, $d$, $s$, $c$, and $b$ quarks with Yukawa coupling constants of order 1. If there are only two light doublets, the doublet orthogonal to the mass-generating combination is likely to couple with the right-handed $b$ quark with a Yukawa coupling constant $\ensuremath{\simeq}\frac{{m}_{t}}{v}$.

Constraints on the weak gauge boson composite scale from the muon g−2 factor

We investigate the contribution of the composite weak gauge and Higgs boson to the g−2 factor of a charged lepton, moving in external magnetic fields. The compositeness of the bosons is treated in the form factor model. The constraints on the boson composite scale from the CERN muon g−2 experimental value and the constraints from the future BNL g−2 measurements are discussed.

Production of composite neutral Higgs bosons in photoproduction and e+e- experiments.

We examine the consequences of a sizable tree-level coupling of a neutral Higgs boson to two photons, which could exist in composite models where the intermediate vector bosons and scalar Higgs bosons are made of the same subconstituents. We find that for certain ranges of the coupling strength and Higgs-boson mass, a neutral composite Higgs boson can be produced and detected in photon-proton scattering and e/sup +/e/sup -/ annihilation at currently accessible energies. We also discuss other processes that are not present in the standard model at the tree level, but may lead to observable neutral-Higgs-boson production at, for instance, a p-barp collider.

Sneaking up on composite models

I discuss the effective low energy theories describing models with a composite Higgs boson and composite fermions in which all explicit global symmetry breaking is done by weak gauge couplings like SU(3) × SU(2) × U(1). In such models, the fermions are lighter than the W and Z by powers of weak gauge couplings. Nontrivial family structure may arise if the theory has a spontaneous broken family symmetry.

Anatomy of a composite Higgs model

In this paper we explain how to construct models where the weak interactions are broken by the composite Higgs mechanism. Such theories differ markedly from SU(2) × U(1) breaking scenarios that involve either fundamental scalars or technicolor. The low-energy spectrum of such theories include a composite Higgs boson, as well as exotic composite scalars and a new massive U(1) gauge boson. We analyze in detail the working of the SU(5)/SO(5) composite Higgs model, previously described by two of the authors, in order to acquaint the reader with the generic traits of such theories.