[en] One of the most interesting classes of processes at high energy e⁺e^--colliders is gauge boson production. We discuss these processes in the energy range from 500 GeV up to 2 TeV, where the associated cross sections are large, i.e. in the pb range. We mainly focus on the process e⁺e^- → W⁺W^- within the Standard Model (SM) at 500 GeV. (orig./HSI)

[en] We describe a formalism for calculating electroweak Sudakov logarithms in the Coulomb gauge. This formalism is applicable to arbitrary electroweak processes. For illustration we focus on the specific reactions e⁺e^- → ff-bar and e⁺e^- → W⁺_TW^-_T, W⁺_LW^-_L, which contain all the salient details of dealing with the various types of particles. We discuss an explicit two-loop calculation and have a critical look at the (non-)exponentiation and factorisation properties of the Sudakov logarithms in the Standard Model

[en] We propose a novel procedure for handling processes that involve unstable intermediate particles. By using gauge-invariant effective Lagrangians it is possible to perform a gauge-invariant resummation of (arbitrary) self-energy effects. For instance, gauge-invariant tree-level amplitudes can be constructed with the decay widths of the unstable particles properly included in the propagators. In these tree-level amplitudes modified vertices are used, which contain extra gauge-restoring terms prescribed by the effective Lagrangians. We discuss the treatment of the phenomenologically important unstable particles, like the top quark, the W- and Z-bosons, and the Higgs boson, and derive the relevant modified Feynman rules explicitly

[en] Radiative corrections to processes that involve the production and subsequent decay of unstable particles are complex due to various theoretical and practical problems. The so-called double-pole approximation offers a way out of these problems. This method is applied to the reaction e⁺e^- → W⁺W^- → 4 fermions, which allows us to address all the key issues of dealing with unstable particles, like gauge invariance, interactions between different stages of the reaction, and overlapping resonances. Within the double-pole approximation the complete O(α) electroweak corrections are evaluated for this off-shell W-pair production process. Examples of the effect of these corrections on a number of distributions are presented. These comprise mass and angular distributions as well as the photon-energy spectrum

[en] We present the distributions for gluon radiation off stop-antistop particles produced in e⁺e^- annihilation: e⁺e^-→ttg. For high energies the splitting functions of the fragmentation process t→tg and g→tt are derived; they are universal and apply also to high-energy stop particles producted at hadron colliders. (orig.)

[en] In this paper we concentrate on the resummation of the 1PI O(α) fermion loops. We try to give some idea of the size of the complete scope of large fermionic corrections. (orig./HSI)

[en] A survey is given of the various aspects of W-boson physics at the next generation of linear colliders. In particular, it is indicated how the W boson can help us improve our understanding of the mechanism of mass generation and the structure of the non-Abelian gauge-boson interactions. Also the topics of radiative corrections and gauge invariance are briefly addressed. (author)

[en] We have determined the QCD corrections to the production of squark-antisquark pairs in p anti p collisions at the Tevatron. If the next-to-leading order corrections are taken into account, the renormalization/factorization scale dependence of the theoretical prediction for the cross section is reduced considerably. The higher order corrections increase the production cross section at the Tevatron by about a factor two if we compare the next-to-leading order prediction at a scale near the sqaurk mass with the lowest order prediction for which, in the experimental analyses, the scale was identified with the invariant energy of the parton subprocess. This results in a rise of the experimental lower bound on the squark mass from the Tevatron by about 20 GeV. (orig.)

[en] A survey is given of the various gauge-invariance-related aspects that play a role when dealing with unstable gauge bosons. (author)

[en] We calculate the virtual electroweak Sudakov (double) logarithms at one- and two-loop level for arbitrary on-shell/on-resonance particles in the Standard Model. The associated Sudakov form factors apply in a universal way to arbitrary non-mass-suppressed electroweak processes at high energies, although this universality has to be interpreted with care. The actual calculation is performed in the temporal Coulomb gauge, where the relevant contributions from collinear-soft gauge-boson exchange are contained exclusively in the self-energies of the external on-shell/on-resonance particles. In view of the special status of the time-like components in this gauge, a careful analysis of the asymptotic states of the theory is required. From this analysis we derive an all-order version of the Goldstone-boson Equivalence Theorem without the need for finite compensation factors. By exploiting conditions obtained from non-renormalization requirements, which are a consequence of our choice of gauge, we show that the Sudakov corrections can be extracted through a combination of energy derivatives and projections by means of external sources. We observe that the Standard Model behaves dynamically like an unbroken theory in the Sudakov limit, in spite of the fact that the explicit particle masses are needed at the kinematical (phase-space) level while calculating the Sudakov form factors