Unweighted event generation in hadronicWZproduction at order(αS)

Abstract

We present an algorithm for unweighted event generation in the partonic process $p\stackrel{\ensuremath{\rightarrow}}{p}{W}^{\ifmmode\pm\else\textpm\fi{}}Z(j)$ with leptonic decays at next-to-leading order in ${\ensuremath{\alpha}}_{\mathrm{S}}.$ Monte Carlo programs for processes such as this frequently generate events with negative weights in certain regions of phase space. For simulations of experimental data one would like to have unweighted events only. We demonstrate how the phase space from the matrix elements can be combined to achieve unweighted event generation using a second stage Monte Carlo integration over a volume of real emissions (jets). Observable quantities are kept fixed in the laboratory frame throughout the integration. The algorithm is applicable to a broader class of processes and is CPU intensive.