QED corrections to the forward backward asymmetry with extraZ bosons fore + e −→f + f −

The complete standard model corrections together with the QED contributions from an additionalZ boson to the forward backward asymmetry of the reactione ⁺ e ^?→(ψ,Z, Z′, ...)→f ⁺ f ⁺ are calculated. They include soft photon exponentiation and a cut on the photon energy. Some numerical applications are considered forE ₆ generated extraZ bosons. Though being small at TRISTAN and LEP1 energies, the QED corrections due toZ′ exchange are very important near and above theZ′ peak.     

High power cryogenic targets

Radiative corrections to parity violating deep inelastic electron scattering (PVDIS) are reviewed including a discussion of the renormalization group evolution (RGE) of the weak mixing angle. Recently obtained results on hypothetical Z?? bosons??for which parity violating observables play an important rôle??are also presented.     

Electroweak radiative corrections to e+e− → Z0Z0

The cross section for e⁺e⁻ → Z⁰Z⁰ with arbitrary polarizations of the leptons and bosons is calculated in the standard electroweak model including the complete one-loop virtual and soft-photon bremsstrahlung corrections. All necessary analytical formulas are presented; numerical results are discussed for the unpolarized case and for the polarization asymmetry. At LEP 200 energies the weak corrections are dominated by the self-energy of the external Z⁰-bosons which contributes about +15%. With increasing energy, the weak corrections decrease up to -18% at 1 TeV due to other contributions.     

Decays of intermediate vector bosons,radiative corrections and QCD jets

We investigate decay properties of the intermediate vector bosons W^± and Z⁰. QED and QCD radiative corrections to leptonic and hadronic decay modes are calculated. Implications of the results for decay widths, branching ratios, determination of the number of neutrino species, e-μ-τ universality and properties of hadronic jets produced in W^± and Z⁰ decays are examined.     

Corrections to the Zτ +τ− vertex in topcolor-assisted technicolor theory

We calculate the corrections to the Zτ⁺τ^? vertex in the one-family topcolor-assisted technicolor models without exact custodial symmetry contributed from the exchange of extended technicolor (ETC) sideways and diagonal gauge bosons and the topcolor gauge boson Z′. The precise measurements of the τ asymmetry parameter Aτ give strong constraint on the free parameters in the topcolor-assisted technicolor models.     

The description of the Kπ = 1+ isovector M1 state within a boson expansion formalism

A nuclear system of Z protons and N neutrons moving in an anisotropic potential well and interacting among themselves through an isoscalar plus an isovector quadrupole-quadrupole interaction is treated within a boson expansion formalism. The expansion is performed in terms of the particle-hole RPA bosons. Application refers to ¹⁵⁶Gd. Appreciable corrections to the RPA results concerning both the energies and the B(M1↑) values are obtained. The higher RPA corrections destroy the fragmentation of the RPA-M1 strength and most of the collectivity is concentrated in one state.     

Cosmological production of vector bosons and cosmic microwave background radiation

An intensive cosmological production of vector W and Z bosons is considered within a cosmological model that involves a relative scale of measurement. Field-theory models are studied in which cosmic microwave background radiation and baryon matter may appear as products of the decay of such primordial bosons.     

Constraints on extended neutral gauge structures

Indirect precision data are used to constrain the masses of possible extra Z^′ bosons and their mixings with the ordinary Z. We study a variety of Z^′ bosons as they appear in E₆ and left-right unification models, the sequential Z boson, and the example of an additional U(1) in a concrete model from heterotic string theory. In all cases the mixings are severely constrained (sinθ<0.01). The lower mass limits are generally of the order of several hundred GeV and competitive with collider bounds. The exception is the Z_ψ boson, whose vector couplings vanish and whose limits are weaker. The results change little when the ρ parameter is allowed, which corresponds to a completely arbitrary Higgs sector. On the other hand, in specific models with minimal Higgs structures the limits are generally pushed into the TeV region.     

Solar neutrinos in models involving an extended Higgs sector

Neutrino oscillations in matter and in a magnetic field are investigated within models involving an extended Higgs sector. The left-right model containing a bidoublet and two triplets of Higgs fields (LRM) and the general two-Higgs-doublet model (GTHDM) are chosen by way of example. It is shown that the interaction of leptons with physical Higgs bosons can substantially change the pattern of oscillations in these models in relation to the predictions of the Standard Model (SM). Upper limits on the Yukawa coupling constants and on the Higgs boson masses are found in order to obtain maximum corrections to the SM solar-matter potential V ^SM. By using constraints on these parameters from the literature and those that are obtained here, it is possible to estimate corrections to V ^SM that come exclusively from charged Higgs bosons. The maximum value of these corrections is 40% of V ^SM within the LRM and 10% of V ^SM within the GTHDM. The entire body of information about the contributions of physical Higgs bosons to the solar-matter potential can be obtained by studying the Lorentz structure of the amplitudes for the reactions e ^? ν _l → e ^? ν _l′ at low energies.     

Production of neutrinos at HERA

For theep collider at HERA, we study processes with neutrinos in the final state. Furthermore, we discuss the production ofW andZ bosons. Because of the very small lifetimes of theW andZ, we consider the production of their leptonic decay products rather than the bosons themselves. All the results are based on exact calculations of the matrix element at the tree level. Total cross sections and various kinematical distributions are presented.     

Effects of strong coupling on pairing fluctuations in layered superconductors

The influence of short inelastic lifetimes due to strong coupling of fermionic quasiparticles to bosons on superconducting fluctuation effects aboveT _c is calculated. Considering a strong-coupling model for a layered superconducting metal, it is shown that pairing fluctuation corrections to the spin-lattice relaxation rate in weak coupling and very strong coupling are qualitatively different if the pairing fluctuation spectrum has s-wave symmetry. For weak coupling the corrections are positive, whereas for very strong coupling γ = 2? d ω α² F(ω)/ω > 2 the corrections are negative. In contrast, the Pauli spin susceptibility is insensitive to strong-coupling corrections.     

Anomalously interacting new extra vector bosons and their first LHC constraints

In this review phenomenological consequences of the Standard Model extension by means of new spin-1 chiral fields with the internal quantum numbers of the electroweak Higgs doublets are summarized. The prospects for resonance production and detection of the chiral vector Z* and W*^± bosons at the LHC energies are considered on the basis of quantitative simulations within the CompHEP/CalcHEP package. The Z* boson can be observed as a Breit-Wigner resonance peak in the invariant dilepton mass distributions in the same way as the well-known extra gauge Z?? bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow one to distinguish them from other heavy neutral resonances. In 2010, with 40 pb^?1 of the LHC proton-proton data at the energy 7 TeV, the ATLAS detector was used to search for narrow resonances in the invariant mass spectrum of e ⁺ e ^? and ??⁺??^? final states and high-mass charged states decaying to a charged lepton and a neutrino. No statistically significant excess above the Standard Model expectation was observed. The exclusion mass limits of 1.15 and 1.35 TeV/c ² were obtained for the chiral neutral Z* and charged W* bosons, respectively. These are the first direct limits on the W* and Z* boson production. Based on the above, a novel strategy for the chiral boson search in the LHC dijet data is discussed. For almost all currently considered exotic models the relevant signal is expected in the central dijet rapidity region y _1,2 ? 0 and |y ₁ ? y ₂| ? 0. On the contrary, the chiral bosons do not contribute to this region but produce an excess of dijet events far away from it. In particular, for these bosons the appropriate kinematical restrictions lead to a dip in the centrality ratio distribution over the dijet invariant mass instead of a bump expected in the most exotic models.     

Spin asymmetries in large-pT production of gauge bosons based on quantum chromodynamics and electroweak gauge model

We make predictions for spin asymmetries in the production of gauge bosons, such as Z⁰, Wsu± and γ, at large p_T from the collision of longitudinally polarized hadrons using QCD perturbation theory and the electroweak gauge model in the framework of a hard scattering model. Asymmetries typically at the 20% and 4% level are predicted for the weak bosons and photon, respectively. Experimental tests should be possible in the near future, e.g., at Fermilab, ISABELLE and colliding SPS.     

Radiative corrections to the scalar Higgs masses in a non-minimal supersymmetric Standard Model

We calculate the dominant one-loop radiative corrections arising from quark-squark loops to the mass squared matrix of theCP-even Higgs bosons in a non-minimal supersymmetric Standard Model containing two Higgs doublets and a Higgs singlet chiral superfield using one-loop effective potential approximation. We use this result to evaluate upper and lower bounds on the radiatively corrected masses of all the scalar Higgs bosons as a function of the parameters of the model. We find that the one-loop radiative corrections are substantial only for the lightest Higgs boson of the model and can push its mass beyond the reach of LEP. We also calculate an absolute upper bound on the mass of the radiatively corrected lightest Higgs boson and compare it with the corresponding bound in the minimal supersymmetric Standard Model.     

The Higgs-photon-Z boson coupling revisited

We analyze the coupling of CP-even and CP-odd Higgs bosons to a photon and a Z boson in extensions, of the Standard Model. In particular, we study in detail the effect of charged Higgs bosons in two-Higgs doublet models;. and the contribution of SUSY particle loops in the minimal supersymmetric extension of the Standard Model: The Higgs-γZ coupling can be measured in the decayZ → γ+Higgs ate ⁺ e ^? colliders running on theZ resonance, or in the reverse process Higgs →Zγ with the Higgs boson produced at LHC. We show that a measurement of this coupling with a precision at the percent level, which could be the case at futuree ⁺ e ^? colliders, would allow to distinguish between the lightest SUSY and standard Higgs bosons in large areas of the parameter space.     

Order αs corrections to intermediate boson masses

We present the order α_s corrections to the masses of the Z and W bosons in the standard model. For the low mass quarks u, d, c and s the corrections are small and positive. Due to the Coulomb singularity which appears in the vector boson self-energy graph with one gluon exchange, we find a negative contribution from the t, b doublets.     

A semi-classical boost-invariant description of pair production in chromoelectric field

The total cross section for the processe ⁺ e ^?→Z ⁰ Z ⁰ followed by the subsequent decay of theZ ⁰-bosons is calculated within the electroweak standard model including one-loop radiative corrections. The effects of the finite width are described in detail. Numerically they are of the order of 10% and thus comparable to the radiative corrections.     

Hadron collider potential for excited bosons search

The e ⁺ e ^? and μ⁺μ^? dilepton final states are the most clear channels for a new heavy neutral resonance search. Their advantage is that usually in the region of expected heavy-mass resonance peak the main irreducible background, from the Standard Model Drell-Yan process, contributes two orders of magnitude smaller than the signal. In this paper we consider the future prospects for search for the excited neutral Z*-bosons. The bosons can be observed as a Breit-Wigner resonance peak in the dilepton invariant mass distributions in the same way as the well-known extra gauge Z′ bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow to distinguish them from the other heavy neutral resonances. At present only the ATLAS Collaboration has looked for such new excitations at the Large Hadron Collider and has published its results for 7 TeV collision energy. After successful comparison of our evaluation with these official results we present our estimations for the discovery potential and the exclusion limits on the Z*-boson search in pp collisions at higher centre-of-mass energies and different luminosities. In particular, LHC Run 2 can discover Z*-boson with its mass up to 5.3 TeV, while the High Luminosity LHC can extend that reach to 6.2 TeV. The High Energy LHC (with collision energy of 33 TeV) will be able to probe two times heavier resonance masses at the same integrated luminosities.     

Two-and three-body decay modes of SUSY Higgs particles

We summarize the dominant decay modes of the neutral and charged Higgs bosons in the Minimal Supersymmetric extension of the Standard Model. While two-body decays are in general dominating, the branching ratios for three-body decays of the heavy scalar, pseudoscalar and charged Higgs bosons can be large below the thresholds if top quarks, W/Z bosons or heavy scalar bosons are involved. Analytical expressions have been derived for the partial decay widths and the physical implications of these decay modes are discussed.     

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.