We test the assumption that fermion-loop corrections to high energy W + W − scattering are negligible when compared to the boson-loop ones. Indeed, we find that, if the couplings of the interactions deviate from their Standard Model values, fermion-loop corrections can in fact become as important or even greater than boson-loop corrections for some particular regions of the parameter space, and both types of loops should be taken into account. Some preliminary results are shown.

The use of Padé approximants for the description of QCD matrix elements is discussed in this talk. We will see how they prove to be an extremely useful tool, specially in the case of resonant amplitudes. It will allow the inclusion of high-energy Euclidian data to improve the determination of low-energy properties, such as the quadratic vector radius. This does not mean that the rational approximations can be arbitrarily employed for the extraction of any desired hadronic parameter. A discussion about the validity, limitations and possible issues of the Padé analysis is carried on along the paper. Finally, based on the de Montessus de Ballore's theorem, a theoretically safe new procedure for the extraction of the pole mass and width of resonances is proposed here and illustrated with the example of the ρ(770).

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This article gives a short overview of the future high-energy e + e − collider projects. Both, linear and circular colliders offer an excellent potential for precision physics and are shortly discussed.