George J Gounaris

Polarization amplitudes fore+e− →W+W− ande+e− →ZZ

The main purpose of this work is to study the three weak boson vertex. We give explicit formulae for all polarization amplitudes of the processese+e− →W+W− ande+e− →ZZ, with arbitrary couplings between the various intermediate vector bosons. Using these expressions we discuss possible signatures ofC, P andT violation in the three vector boson coupling, as well as the effects of anomalous magnetic dipole and electric quadrupole moments ofW±. The amplitudes for the above processes in any SU(2) × U(1) and SU(2)L × SU(2)R × U(1) gauge theory are also given, while the special case of the Weinberg-Salam model is studied in detail.

The

Abstract. We study the helicity amplitudes of the process

\gamma \gamma \to \gamma \gamma

\gamma \gamma \to \gamma \gamma

process in the standard and SUSY models at high energies

at high energy, which in the standard and SUSY models first arise at the one-loop order. In the standard model (SM), the diagrams involve

Duality in the current propagator

W

On the radiative corrections to the electroweak parameters and precision tests of the electroweak theory

, charged-quark, and lepton loops, while in SUSY, we also have contributions from chargino-, charged-sfermion, and Higgs-loop diagrams. The SUSY contributions are most important in the region above the threshold for producing the supersymmetric partners; there, they interfere most effectively with the primarily imaginary SM amplitudes. Simple expressions for the relevant one-loop functions are given which provide a direct overview of the behaviour of the helicity amplitudes in the whole parameter space at high energies. The various characteristics of a large set of observables are studied in detail.

Current propagator: Duality between vector mesons and perturbative QCD

Abstract The idea of local duality between generalized vector dominance and light cone algebra or parton model is applied to the propagator of vector currents. A set of sum rules reminiscent of the generalized first Weinberg sum rules but involving certain unknown parameters are derived. These parameters are fixed from the leptonic decay modes of ϱ, ω, ϕ. The sum rules are used to calculate the ω-ϕ mixing angle and thereby predict Γ(ϕ→ K K ) = 3.24±0.34 MeV , in agreement with experiment. Simple mass mixing or current mixing model for the vector mesons seem to be inconsistent with data. The total cross section for e + e − →hadrons is calculated in the scaling region. If scaling is achieved at s ⋍ 9–16 GeV 2 then it is argued that about 22% of the events in this energy region will include strange particles.

A method to calculate subtraction constants application to the η → π° γγ problem

The radiative corrections to the electroweak parameters are reconsidered with an emphasis on analysing prospects for future tests of the as yet untested parts of the electroweak theory, in particular the “new physics” of vector-boson self-interactions and the Higgs scalar. The vacuum polarization due to the light fermions is treated in the leading-long approximation, while the top-quark is taken into account exactly. A detailed analysis of the errors involved in our approximations and a comparison with the results of complete one-loop calculations shows that vacuum polarization due to bosons is negligible, ifmH=100 GeV, while it may become visible in precision tests ine+e− annihilation, ifmH≅1 TeV. We also give detailed results (as a function of the top-quark mass) on the radiatively correceted parameters used in model-independent fits to neutrino-scattering and in the interpretation of atomic-parity violation experiments. Technically, we diagonalize the γ-Z propagator for anyq2, and we show, when treating the top-quark vacuum polarization exactly, that the intuitively appealing notion of running coupling constants can be used beyond the leading-log approximation.

A FORTRAN code for gammagamma-->ZZ in SM and MSSM

Local duality between vector mesons and perturbative QCD in the current propagator supplies expressions for their leptonic widths in terms of the quark masses, the masses of the lowest vector mesons and their first excitations and the QCD parameter Λ. The experimental data are consistent with this physical principle if ϱ′(1260 MeV) exists.

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It is demonstrated that the duality finite energy sum rule method to take into account high mass contributions to amplitudes at low energy and momentum transfer essentially determines the subtraction constant. The method therefore has to be used whenever one of the amplitudes does not accept unsubtracted dispersion relations. Using this method we predict [γ(η → πoγγ)][γ(η → 2γ)] = (5 ± 3)%. Such a result seems to be favoured by recent experiments and moreover is bigger by a factor 80 than the usual vector meson dominance prediction. Comments about ω → 3π and X → πoγγ are also made.