The Matrix Element Method at Next-to-Leading Order

TL;DR

This paper extends the matrix element method to next-to-leading order in perturbation theory, enabling more precise likelihood calculations and efficient event generation for particle physics analyses.

Contribution

It introduces a novel method to compute NLO weights event-by-event, allowing NLO likelihoods and unweighted event generation within the matrix element framework.

Findings

Successful application to Z boson mass measurement

Effective search for Higgs boson in four lepton channel

Enhanced precision in particle physics analyses

Abstract

This paper presents an extension of the matrix element method to next-to-leading order in perturbation theory. To accomplish this we have developed a method to calculate next-to-leading order weights on an event-by-event basis. This allows for the definition of next-to-leading order likelihoods in exactly the same fashion as at leading order, thus extending the matrix element method to next-to-leading order. A welcome by-product of the method is the straightforward and efficient generation of unweighted next-to-leading order events. As examples of the application of our next-to-leading order matrix element method we consider the measurement of the mass of the Z boson and also the search for the Higgs boson in the four lepton channel.