arXiv subjects
Publications and source records attributed to Michael Kobel.
This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.
This report summarizes the results of the two-fermion working group of the LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the theoretical calculations of the two fermion production process in the electron-positron collision at LEP2 center of the mass energies are reported. The Bhabha process and the production of muon, tau, neutrino and quark pairs is covered. On the basis of comparison of various calculations, theoretical uncertainties are estimated and compared with those needed for the final LEP2 data analysis. The subjects for the further studies are identified.
Recent LEP results on single and pair production of neutral electroweak gauge bosons are reviewed. QED and Electroweak gamma-e Compton scattering at LEP covers gamma-e center-of-mass energies sqrt{shat} in the range from about 20 GeV to 170 GeV, and leads to single production of on-shell gamma, off-shell gamma*, and Z bosons, also known as ``Zee'' process. The latter two final states have been observed for the first time by the OPAL collaboration, while the measurement of the scattered on-shell gamma's by L3 represents the highest energies at which QED Compton scattering has been studied so far. These processes can be used to set limits on excited electrons. Pair production of gamma* and/or Z at the e+e- center-of-mass energy sqrt{s}=183 GeV has been studied by the DELPHI, L3, and OPAL collaborations. The combination of these experiments yields the first significant measurement of Z pair production. With more statistics at higher energies, interesting limits on anomalous gammaZZ and ZZZ couplings can be derived from this process.
Four-fermion production via electroweak neutral currents has been measured by all four LEP collaborations at center-of-mass energies near the Z resonance and for the first time also at energies well above the Z peak. Essentially all possible final states have been covered in four different topologies.