Olga Bessidskaia Bylund (Stockholm University (SE))
The large integrated luminosity provided by the LHC enables the production significant numbers of top quark pairs in association with addition jets or additional gauge bosons. The production crosssection of topquark pairs in association with jets originating from additional bquarks is presented. This process is an important background to searches for new physics and is compared to the available theoretical calculations. In addition, the production of top quark pairs in association with W and Z bosons is presented. The measurement uses events with multiple leptons and in particular probes the coupling between the top quark and the Z boson. Finally, the crosssection measurement of photons produced in association with top quark pairs is presented. The measurement uses a data driven technique to extract the signal from the background and achieves a significance of greater than 5 standard deviations.
Judith Katzy (DESY, HAMBURG)