Monte-Carlo event generation for the LHC

This thesis discusses recent developments for the simulation of particle physics in the light of the start-up of the Large Hadron Collider. Simulation programs for fully exclusive events, dubbed Monte-Carlo event generators, are improved in areas related to the perturbative as well as non-perturbative regions of strong interactions. A short introduction to the main principles of event generation is given to serve as a basis for the following discussion. An existing algorithm for the correction of parton-shower emissions with the help of exact tree-level matrix elements is revisited and significantly improved as attested by first results. In a next step, an automated implementation of the POWHEG method is presented. It allows for the combination of parton showers with full next-to-leading order QCD calculations and has been tested in several processes. These two methods are then combined into a more powerful framework which allows to correct a parton shower with full next-to-leading order matrix elements and higher-order tree-level matrix elements at the same time. Turning to the non-perturbative aspects of event generation, a tuning of the Pythia event generator within the Monte-Carlo working group of the ATLAS experiment is presented. It is based on early ATLAS minimum bias measurements obtained with minimal model dependence. The parts of the detector relevant for these measurements are briefly explained. Throughout the thesis, results obtained with the improvements are compared to experimental measurements.