Generation cuts and Born suppression in POWHEG
Paolo Nason, Carlo Oleari
TL;DR
The paper addresses spikes in dijet distributions that arise after POWHEG showering when using Born suppression. It introduces a practical fix (doublefsr=1) that includes both quark- and gluon-initiated splittings with symmetric suppression to avoid large-weight configurations, and proposes a recomputed scalup (RS) prescription to further stabilize the output. Numerical studies at LHC7 TeV show reduced spikes and improved robustness when applying these features, validating their recommended use for dijet production. Collectively, the work enhances the reliability of POWHEG BOX predictions by refining singular-region treatment and shower interfacing.
Abstract
In this short note we discuss the origin of spikes in physical distributions in dijet production, originating after the Monte Carlo shower of POWHEG Les Houches events. We introduce a refinement of the way in which the POWHEG BOX separates the singular regions that reduces the appearance of spikes in the computed distributions. We also study the sensitivity of the results due to a modification of the way the POWHEG events are passed to the shower Monte Carlo program. We recommend that the new features should be used always in dijet production.