AbstractsPhysics

The Drell-Yan-like production of electroweak gauge bosons with the subsequent decay into lepton pairs represents one of the most prominent processes at the LHC. Apart from being an important standard candle and an irreducible background in the search for new gauge bosons in the high-energy regime, these processes allow for high-precision measurements in the resonance region: The weak mixing angle might be extracted with LEP precision and the W-boson mass is expected to be measured with the highest accuracy ever. In order to fully exploit the experimental accuracy that is achievable for the Drell-Yan process, precise theoretical predictions are mandatory. In view of fixed-order calculations, the main theoretical uncertainties arise from the unknown mixed QCD-electroweak radiative corrections of order O(as a). In this work, we establish a framework for the calculation of the O(as a) corrections to Drell-Yan processes in the pole approximation (PA). It is based on a systematic expansion of the cross section about the resonance pole and aims at improving the theoretical prediction in the vicinity of the gauge-boson resonance where the higher precision is especially relevant. The PA further decomposes the corrections into distinct well-defined parts in terms of factorizable and non-factorizable corrections. In the former, the production and decay of the gauge boson proceed independently, whereas in the latter, the production and decay sub-processes are linked by soft-photon exchange. We first apply the PA to the electroweak next-to-leading order corrections in order to establish our methods and to assess the quality of the approximation by a detailed comparison to the known full results. For a consistent application of the PA to all parts of the calculation, in particular also the real-emission corrections, the dipole subtraction formalism is extended to cover decay kinematics, which has not been considered in the literature so far. At O(as a), we describe the concept of the expansion and first discuss the calculation of the non-factorizable contributions, which turn out to be phenomenologically negligible. This result demonstrates that the O(as a) corrections almost entirely result from the contributions where the production and decay of the W/Z boson proceed independently. We explicitly compute the factorizable corrections of “initial-final” type, which we expect to be the dominant contribution at the order O(as a), and compare our results to different versions of a naive product ansatz. Our results are implemented in a flexible Monte Carlo program which allows to compute total cross section predictions as well as arbitrary differential distributions and that can be used in the analysis of LHC data. Die Produktion von W- und Z-Bosonen über den Drell-Yan Prozess stellt eine wichtige Klasse von Referenzprozessen am LHC dar. Er ist ein irreduzibler Hintergrundprozess in der Suche nach neuen schweren Eichbosonen und erlaubt darüber hinaus eine präzise Messung des effektiven schwachen Mischungswinkels und der W-Boson…