Sequential W and Z bosons

We present and discuss a class of electroweak gauge models where the low-energy phenomenology is naturally identical to that of the standard model, but which allows for the existence of an arbitrary number of weak gauge bosons which have nontrivial couplings to the known fermions. The lightest W and Z in these models must be lighter than the W and Z of the standard model.     

Doubly charged Higgs bosons

We explore through two simple models, the first in which scalars are treated as fundamental and the second in which they are composite objects, the possibility that representations containing doubly charged scalars may participate in the spontaneous breakdown of the SU(2) × U(1) symmetry of electroweak interactions. We show that such exotic Higgs bosons may posses unsuppressed coupling to pairs of gauge vector bosons and comment on the observability of these charged Higgs bosons through the Cahn-Dawson mechanism in high-energy hadron colliders.     

Excited weak vector bosons facing the high energy and high precision frontier

If the recently discovered weak bosons W^± and Z were manifestations of a composite structure of the weak interactions rather than the commonly assumed gauge bosons of a fundamental gauge symmetry one is naturally led to expect a corresponding spectrum of excited weak vector bosons. Experiments at LEP I/SLC and LEP II may be uniquely suited to shed light on this question with their power to perform high precision tests of the standard model.     

Corrections to Z Hadronic Decays From Composite Model

Ne assume that the gauge bosons W and Z are composed of subconstituents. The generalized form for Hung-Sakurai model is obtained in the existence of the exciting states of W and Z bosons. It is shown that the predictioh for the Z hadronic width is smaller than that of standard model since the gauge coupling constant decreases in the composite model. One-loop contributions from the exciting states are also discussed.     

Non standard weak bosons at HERA collider

We compare the effects of non-standard weak bosons (NSB) expected fromE ₆-superstrings (Z′), strong Higgs (V ₀) and composite (spin 0, 1, 2) models by using the classical inclusive deep-inelastic “ep” scattering at HERA energies. TheX ² associated to polarized and unpolarized cross-sections, as well as the six combinations of asymmetries, allow us to derive significant bounds on the masses of the new bosons of various spins associated to some composite models with exception of the excitedZ ^*. We have also obtained some lower bounds for spin one bosons of different models (Z′,V ₀,Z ^*) which are stronger than the present experimental limits.     

Chiral bosons

The local lagrangian formulation for chiral bosons recently suggested by Floreanini and Jackiw is analyzed. We quantize the system and explain how the unconventional Poincaré generators of left and right chiral bosons combine to form the standard generators. The left-U(1) Kac-Moody algebra and the left-Virasoro algebra are shown to be the same as for left Weyl fermions. We compare the partition functions, on the torus, of a chiral boson and a chiral fermion. The left-moving boson is coupled to gauge fields producing the same anomalies as in the fermionic formulation. It is pointed out that the unconventional Lorentz transformations are inapplicable for the coupled system and a set of different transformations is presented. A coupling to gravity is proposed. We present the theory of chiral bosons on a group manifold, the chiral WZW model. The (1,0) supersymmetric abelian and non-abelian chiral bosons are described.     

Landau-Yang theorem and decays of a Z' boson into two Z bosons

We study the decay of a Z' boson into two Z bosons by extending the Landau-Yang theorem to a parent particle decaying into two Z bosons. For a spin-1 parent the theorem predicts that (1) there are only two possible couplings and (2) the normalized differential cross section depends on kinematics only through a phase shift in the azimuthal angle between the two decay planes of the Z boson. When the parent is a Z' the two possible couplings are anomaly induced and CP violating, respectively. At the CERN Large Hadron Collider their effects could be disentangled when both Z bosons decay leptonically.     

Bose-Einstein correlations of neutral gauge bosons in pp collisions

The theory for Bose-Einstein correlations in case of neutral gauge bosons in pp collisions at high energies is presented. Based on quantum field theory at finite temperature, the two-particle Bose-Einstein correlations of neutral gauge bosons are carried out for the first time. As a result, the important parameters of the correlation functions can be obtained for the Z ⁰ Z ⁰ pairs. The article is published in the original.     

The decays of on-shell and off-shell polarized gauge bosons into massive quark pairs at NLO QCD

We discuss the polar angle decay distribution in the decay of on-shell and off-shell polarized (W, Z) gauge bosons into massive quark pairs. In particular for the off-shell decays in $H \to \left( {W,Z} \right) + \left( {W^* ,Z^* } \right)\left( { \to q_1 ,\vec q_2 } \right)$ it is important to keep the masses of the charm and bottom quarks at their finite values since the scale of the problem is not set by m _W,Z ² but by the offshellness of the gauge boson which varies in the range (m ₁ + m ₂)² ≤ q ² ≤ (m _H ? m _W,Z )².     

Looking for new gauge bosons in radiative decays of pseudoscalar mesons

We perform the model independent analysis of possibilities of looking for new gauge bosons in radiative decays of π⁰, η, η′ mesons. For this purpose we consider various experimental constraints on properties of light gauge bosons. It is shown that the branching ratios of these decays can be as large as: BR(π⁰→γ+X)?10^?3, BR(η→γ+X)?10^?4, BR(η′→γ+X)?10^?6, what is highly interesting from the experimental point of view.     

Strangephilic Higgs bosons in the MSSM

We suggest a new CPX-derived scenario for the search for strangephilic MSSM Higgs bosons at the Tevatron and the LHC, in which all neutral and charged Higgs bosons decay predominantly into pairs of strange quarks and into a strange and a charm quark, respectively. The proposed scenario is realized within a particular region of the MSSM parameter space and requires large values of tan?β, where threshold radiative corrections are significant to render the effective strange-quark Yukawa coupling dominant. Experimental searches for neutral Higgs bosons based on the identification of b-quark jets or τ leptons may miss a strangephilic Higgs boson and its existence could be inferred indirectly by searching for hadronically decaying charged Higgs bosons. Potential strategies and experimental challenges to search for strangephilic Higgs bosons at the Tevatron and the LHC are discussed.     

Search for new neutral gauge bosons at LHC

New heavy gauge bosons belonging to an extended (in relation to the Standard Model) gauge sector are present in Grand Unified Theories, as well as in a number of models aimed at solving the hierarchy problem—in particular, in the technicolor model and in some versions of multidimensional field theories (for example, in the Little Higgs model). The LHC potential for seeking new neutral gauge bosons in decays to two muons is studied.     

Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model at the LHC

We review possible properties of Higgs bosons in the NMSSM, which allow to discriminate this model from the MSSM: masses of mostly Standard-Model-like Higgs bosons at or above 140 GeV, or enhanced branching fractions into two photons, or Higgs-to-Higgs decays. In the case of a Standard-Model-like Higgs boson above 140 GeV, it is necessarily accompanied by a lighter state with a large gauge singlet component. Examples for such scenarios are presented. Available studies on Higgs-to-Higgs decays are discussed according to the various Higgs production modes, light Higgs masses and decay channels.     

Pseudoscalar Higgs bosons at the LHC: production and decays into electroweak gauge bosons revisited

We analyse and compute, within a number of standard model (SM) extensions, the cross sections σ _A→VV′ for the production of a heavy neutral pseudoscalar Higgs-boson/spin-zero resonance at the LHC and its subsequent decays into electroweak gauge bosons. For comparison we calculate also the corresponding cross sections for a heavy scalar. The SM extensions we consider include a type-II two-Higgs doublet model (2HDM), a 2HDM with four chiral fermion generations, the minimal supersymmetric extension of the SM (MSSM), and top-colour assisted technicolour models. Presently available phenomenological constraints on the parameters of these models are taken into account. We find that, with the exception of the MSSM, these models permit the LHC cross sections σ _A→VV′ to be of observable size. That is, a pseudoscalar resonance may be observable, if it exists, at the LHC in its decays into electroweak gauge bosons, in particular in WW and γ γ final states.     

Heavy SUSY Higgs bosons at e + e − linear colliders

The production mechanisms and decay modes of the heavy neutral and charged Higgs bosons in the Minimal Supersymmetric Standard Model are investigated at future e ⁺ e ^? colliders in the TeV energy regime. We generate supersymmetric particle spectra by requiring the MSSM Higgs potential to produce correct radiative electroweak symmetry breaking, and we assume a common scalar mass m₀, gaugino mass m_1/2 and trilinear coupling A, as well as gauge and Yukawa coupling unification at the Grand Unification scale. Particular emphasis is put on the low tan β solution in this scenario where decays of the Higgs bosons to Standard Model particles compete with decays to supersymmetric charginos/neutralinos as well as sfermions. In the high tan β case, the supersymmetric spectrum is either too heavy or the supersymmetric decay modes are suppressed, since the Higgs bosons decay almost exclusively into b and τ pairs. The main production mechanisms for the heavy Higgs particles are the associated AH production and H ⁺H^? pair production with cross sections of the order of a few fb.     

Difficulties for five-dimensional gauge-higgs unification

We consider five-dimensional gauge theories where all fields propagate in the bulk and the fifth direction is compactified on the orbifold S1/Z2, and where the fifth components of the gauge bosons play the role of the standard model Higgs boson (gauge-Higgs unification). The gauge symmetry breaking is realized through the appropriate orbifold boundary conditions and through the Hosotani mechanism. We show that for any such theory (with neither brane gauge kinetic terms nor anomalous gauge-group factors) the assumption that the low-energy vector-boson spectrum consists of the W(+/-), Z, and gamma only, is inconsistent with the experimental requirements sin2thetaW approximately 1/4 and rho identical with mW2/(mZ2 cos2theta w) = 1.     

Photoproduction of vector and Higgs scalar bosons on an electron

We consider the photoproduction processes, introduced in the SU(2)×U(1) theory, whereby vector W and Z and scalar bosons are produced on an electron. The differential cross sections for the distribution of the leptons and bosons produced as well as the total cross sections of the processes, are calculated and analyzed. The asymptotic values of the total cross section are also given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–50, April, 1984.     

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.     

Non-abelian gauge bosons in the compactified bosonic membrane theory

We consider the bosonic membrane compactified on a torus. The membrane motion is stabilized by a topologically non-trivial background. We find that, in the narrow membrane limit, the mass formula to O(ħ;) reduces to exactly the same form as that of the compactified closed bosonic string theory, and we obtain (almost) massless vector bosons in the adjoint representation of a simply laced Lie group in D = 27. This is only dimension at which the gravitation and gauge bosons may coexist in that background.     

Electroweak precision data and right-handed gauge bosons

The implication of recent electroweak precision data for left-right symmetric models is examined. We establish a lower bound on the charged and neutral right-handed gauge bosons independent of the right-handed neutrino mass and of any restrictions or implied symmetries on the right KM matrix.