Combining QCD Matrix Elements at Next-to-Leading Order with Parton Showers

We present a general method to combine next-to-leading order (NLO) matrix elements in QCD with leading logarithmic parton showers by applying a suitably modified version of the phase-space-slicing method. The method consists of subsuming the NLO corrections into a scale-dependent phase-space-slicing parameter, which is then automatically adjusted to cut out the leading order, virtual, soft and collinear contributions in the matrix element calculation. In this way the two main obstacles for matching matrix elements with parton showers, namely the problem of double counting and of negative weights, are removed. As an example, we display the method for single-jet inclusive cross sections at O(αs) in electroproduction. We numerically compare the modified version of the phase-space-slicing method with the standard approach and find very good agreement on the percent level.