Abstract:The complete matrix elements for e + e − → 4f and e + e − → 4f γ are calculated in the Electroweak Standard Model for polarized massless fermions. The matrix elements for all final states are reduced to a few compact generic functions. Monte Carlo generators for e + e − → 4f and e + e − → 4f γ are constructed. We compare different treatments of the finite widths of the electroweak gauge bosons; in particular, we include a scheme with a complex gauge-boson mass that obeys all Ward identities. The detailed discussion of numerical results comprises integrated cross sections as well as photon-energy distributions for all different final states.

Abstract:RacoonWW is an event generator for e + e − → WW → 4 fermions(+γ) that includes full tree-level predictions for e + e − → 4f and e + e − → 4f + γ as well as O(α) corrections to e + e − → 4f in the so-called double-pole approximation. We briefly sketch the concept of the calculation on which this generator is based and present some numerical results. Abstract. RacoonWW is an event generator for e + e − → WW → 4 fermions(+γ) that includes full tree-level predictions for e + e − → 4f and e + e − → 4f + γ as well as O(α) corrections to e + e − → 4f in the so-called double-pole approximation. We briefly sketch the concept of the calculation on which this generator is based and present some numerical results.

The O͑␣͒ electroweak radiative corrections to the process p p h→W Ϯ →l Ϯ (l ϭe,) are calculated. The O͑␣͒ corrections can be decomposed into separate gauge invariant contributions to the W boson production and decay processes. Factorizing the collinear singularity associated with initial state photon radiation into the parton distribution functions, we find that initial state corrections have a significantly smaller effect than final state radiative corrections. We study in detail the effect of electroweak radiative corrections on a number of interesting observables: the W transverse mass distribution, the W to Z transverse mass ratio, the charge asymmetry of leptons in W→l decays, as well as the W production cross section and the W to Z cross section ratio. We also investigate how experimental lepton identification requirements change the effect of the electroweak corrections.

We calculate the complete electroweak O(α) corrections to p p (−) → l + l − X(l = e, µ) in the Standard Model (SM) of electroweak interactions. They comprise weak and photonic virtual one-loop corrections as well as real photon radiation to the parton-level processes qq → γ, Z → l + l − . We study in detail the effect of the radiative corrections on the l + l − invariant mass distribution, the cross section in the Z boson resonance region, and on the forward-backward asymmetry, A FB , at the Fermilab Tevatron and the CERN Large Hadron Collider. The weak corrections are found to increase the Z boson cross section by about 1%, but have little effect on the forward-backward asymmetry in the Z peak region. Threshold effects of the W box diagrams lead to pronounced effects in A FB at m(l + l − ) ≈ 160 GeV which, however, will be difficult to observe experimentally. At high di-lepton invariant masses, the non-factorizable weak corrections are found to become large.

Physics at the Large Hadron Collider (LHC) and the International e + e − Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined.4