Phase space veto method for next-to-leading order event generators in hadronic collisions

Abstract

A method for organizing next-to-leading order QCD calculations using a veto which enforces the cancellations between virtual and real emission diagrams is applied to hadronic collisions. The method employs phase space slicing with the slicing parameter determined dynamically event-by-event. It allows for the generation of unweighted events and can be consistently merged with a parton shower. The end product is more intuitive for the end user, as it is probabilistic, and can be easily interfaced to general purpose showering and hadronization programs to obtain a complete event description suitable for experimental analyses. As an example an event generator for the process pp --> Z + X at NLO is presented and interfaced consistently to the PYTHIA shower and hadronization package.