Merging meets matching in MC@NLO

TL;DR

This paper develops a merging procedure for MC@NLO simulations to accurately predict observables with different light-jet multiplicities, demonstrated with LHC processes involving Higgs, leptons, and top pairs.

Contribution

It introduces a new merging method for MC@NLO that can be integrated into existing frameworks, improving predictions across multiple jet multiplicities.

Findings

Successfully implemented the merging procedure in aMC@NLO

Applied method to LHC processes with up to 2 jets

Enhanced accuracy of exclusive jet predictions

Abstract

The next-to-leading order accuracy for MC@NLO results exclusive in J light jets is achieved if the computation is based on matrix elements that feature J and J+1 QCD partons. The simultaneous prediction of observables which are exclusive in different light-jet multiplicities cannot simply be obtained by summing the above results over the relevant range in J; rather, a suitable merging procedure must be defined. We address the problem of such a merging, and propose a solution that can be easily incorporated into existing MC@NLO implementations. We use the automated aMC@NLO framework to illustrate how the method works in practice, by considering the production at the 8 TeV LHC of a Standard Model Higgs in association with up to J=2 jets, and of an e\nu_e pair or a t\bar{t} pair in association with up to J=1 jet.