Ansgar Denner

Electroweak radiative corrections to e+e− → W+W−

The cross section for e+e− → W+W− 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. The relevant analytic results are listed and the influence of the radiative corrections on the unpolarized cross section is discussed. We find moderate corrections at LEP II energies. The corrections increase continuously with energy up to − 50% of the Born cross section at 1 TeV.

Scalar one-loop 4-point integrals

Abstract We provide a complete set of results for the scalar 4-point function appearing in one-loop calculations in QCD, QED, the electroweak Standard Model and popular extensions thereof. Complex internal masses, which are needed for calculations involving unstable particles, are supported throughout, whereas complex momenta are not supported. In particular, for the most general, regular case we present two independent results in terms of 72 and 32 dilogarithms. In addition we list explicit results for all soft- and/or collinear-singular cases in dimensional regularization, mass regularization, and in regularizations of mixed type. The exceptional case with a vanishing modified Cayley determinant, which hardly appears in applications, is not considered.

Infrared divergent scalar box integrals with applications in the electroweak standard model

Abstract General IR-divergent scalar box integrals, as present in calculations of radiative corrections, are calculated, using a photon mass λ as regulator. Also special “mass singular” cases and examples thereof occuring in the electroweak theory are listed. It is also shown how these IR-divergent integrals appear in the reduction of the corresponding tensor integrals.

COLLIER - A fortran-library for one-loop integrals

We introduce the fortran-library COLLIER for the numerical evaluation of one-loop scalar and tensor integrals in perturbative relativistic quantum field theories. Important features are the implementation of dedicated methods to achieve numerical stability for 3- and 4-point tensor integrals, the support of complex masses for internal particles, and the possibility to choose between dimensional and mass regularization for infrared singularities. COLLIER supports one-loop N-point functions up to currently N=6 and has been tested in various NLO QCD and EW calculations.

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.

EW corrections to Higgs strahlung at the Tevatron and the LHC with HAWK

We briefly report on the inclusion of NLO QCD and electroweak corrections to the Higgsstrahlung processes pp/p p→ HW/Z → H+ 2leptons in the Monte Carlo program HAWK†. The electroweak corrections, which are at the level of −(5−10)% for total cross sections, further increase in size with increasing transverse momenta (pT) in differential cross sections. For instance, for pT,H ∼ 200GeV, which is the interesting range at the LHC, the electroweak corrections to WH production reach about −15% for MH = 120GeV.

EW and QCD One-Loop Amplitudes with RECOLA

We present the computer code RECOLA for the computation of EW and QCD amplitudes in the Standard Model at next-to-leading order. One-loop amplitudes are represented as linear combinations of tensor integrals whose coefficients are calculated by means of recursive relations similar to Dyson-Schwinger equations. A novel treatment of colour enables us to recursively construct the colour structure of the amplitude efficiently. R ECOLA is linked with the library COLLIER for the computation of the tensor integrals.

Green functions from a gauge-invariant effective action for the electroweak Standard Model

Abstract Application of the background-field method to the electroweak Standard-Model yields a gauge-invariant effective action giving rise to simple Ward identities. We find that in the backgroun-field t Hooft-Feynman gauge the resulting vertex functions are exactly those that are obtained using the pinch technique. Thus, the background-field method provides a general framework that generalizes the pinch technique directly and uniquely to arbitrary Green functions and arbitrary orders of perturbation theory. Moreover, the desirable properties of the pinch-technique vertex functions hold for arbitrary gauge parameters and have a simple explanation within the background-field method.Application of the background-field method to the electroweak Standard-Model yields a gauge-invariant effective action giving rise to simple Ward identities. We find that in the background-field `t Hooft-Feynman gauge the resulting vertex functions are exactly those that are obtained using the pinch technique. Thus, the background-field method provides a general framework that generalizes the pinch technique directly and uniquely to arbitrary Green functions and arbitrary orders of perturbation theory. Moreover, the desirable properties of the pinch-technique vertex functions hold for arbitrary gauge parameters and have a simple explanation within the background- field method.

Electroweak corrections to vector-boson scattering

We report on a recent calculation of the complete NLO QCD and electroweak corrections to the process

Electroweak corrections to gauge-boson pair production processes at the LHC including leptonic W/Z decays

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