Infrared structure of e+e−→3e^+e^- \to 3 jets at NNLO: QED-type contributions

The NNLO QCD corrections to the $e^+e^- \to 3$ jets can be decomposed according to their colour factors. Out of the seven colour factors, three are of QED-type: $1/N^2$, $N_F/N$ and $N_F^2$. We use the antenna subtraction method to compute these contributions, providing complete expressions for the subtraction terms in $N_F/N$ and $N_F^2$.Comment: Talk presented at Loops and Legs 2006, Eisenac

Isolated Photons in Deep Inelastic Scattering

Photon radiation at large transverse momenta at colliders is a detailed probe of hard interaction dynamics. The isolated photon production cross section in deep inelastic scattering was measured recently by the ZEUS experiment, and found to be considerably larger than theoretical predictions obtained with widely used event generators. To investigate this discrepancy, we perform a dedicated parton-level calculation of this observable, including contributions from fragmentation and large-angle radiation. Our results are in good agreement with all aspects of the experimental measurement.Comment: 4 pages, 3 figure

Deep-inelastic Electron-Photon Scattering at High Q^2 : Neutral and Charged Current Reactions

We present the results of a calculation of deep inelastic electron-photon scattering at a linear collider for very high virtuality of the intermediate gauge boson up to NLO in perturbative QCD. The real photon is produced unpolarized via the Compton back scattering of laser light of the incoming beam. For $Q^2$ values close to the masses squared of the Z and W gauge bosons, the deep inelastic electron-photon scattering process receives important contributions not only from virtual photon exchange but also from the exchange of a Z-boson and a W-boson. We find that the total cross section for center of mass energies above $500 \rm{GeV}$ is at least of ${\cal O}(pb)$ and has an important charged current contribution.Comment: Talk given at the International Conference on the Structure and Interactions of the Photon, PHOTON 99, Freiburg im Breisgau, Germany, May 23-27, 1999. To be published in the Proceedings. 6 pages, 6 postscript figures. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ttp99/ttp99-30/ or via www at http://www-ttp.physik.uni-karlsruhe.de/Preprints