Event Generators and Resummation

The workshop is jointly organized by the Monte Carlo Group of DESY Analysis Center and the Particle Physics Group of University of Manchester. At the LHC, QCD effects are crucial in the production and/or decay of the particles being measured or sought and in calculating the (often huge) backgrounds. A precise understanding of and ability to calculate QCD contributions is therefore vital to the success of the LHC. With regard to high multiplicity final states, in particular, one has two main approaches: general purpose Monte Carlo algorithms and analytical resummation methods. The Monte Carlos try to simulate high multiplicity event in a fully exclusive way including the summation of large logarithms via the use of a parton shower. Unfortunately the accuracy of this summation is not entirely clear beyond the control of leading logarithmic terms. On the other hand analytic resummation programs make precise predictions by summing up large logarithms at least at next-to-leading logarithmic level but can be performed for a relatively small class of observables.