The Matrix Element Method at next-to-leading order QCD for hadronic collisions: single top-quark production at the LHC as an example application

Abstract

Recently, a general algorithm to extend the Matrix Element Method (MEM) by taking into account next-to-leading-order (NLO) corrections in quantum chromodynamics (QCD) has been presented. In this article, the algorithm is applied to the most general case that coloured partons are encountered in the initial as well as the final state. This represents a substantial extension compared to previous work. As a concrete example, the production of single top quarks at the LHC is studied. We present in detail the generation of unweighted events following the NLO predictions. By treating these events as the result of a toy experiment, we show the first proof-of-principle application of the Matrix Element Method at NLO QCD for hadronic jet production. As an illustration, we study the determination of the top-quark mass. We find that-apart from elevating the powerful MEM to a sound theoretical foundation at NLO-the inclusion of the NLO corrections can lead to sizeable effects compared to the Matrix Element Method relying on leading-order predictions only. Furthermore, we find that the incorporation of the NLO corrections is mandatory to obtain reliable estimates of the theoretical uncertainties. In addition, this work shows that measuring the top-quark mass using the MEM in single top-quark production offers an interesting alternative to mass measurements in top-quark pair production. * Till.Martini@physik.hu-berlin.de † Peter.Uwer@physik.hu-berlin.de

MadMiner: Machine Learning-Based Inference for Particle Physics

“…In this approximation, the likelihood becomes tractable. This category includes the Matrix Element Method [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], Optimal Observables [27][28][29], and Shower and Event Deconstruction [30][31][32][33]. These methods make maximal use of the knowledge about the physics underlying the simulations.…”

How to GAN away detector effects

“…This would also allow us to directly compare first-principles QCD predictions with modern LHC measurements. In addition, our fast inversion might help with advanced statistical techniques like the matrix element method [29][30][31][32][33][34].…”

Matrix element method at NLO for (anti-) kt -jet algorithms

“…As a proof of concept, the method has been applied in ref. [38] to hadronic single top-quark production-a process where the Matrix Element Method has been used from early days on to disentangle the signal from an overwhelming background [39].…”

“…[37] and ref. [38] to simulate a toy experiment and to validate the approach. These events obviously depend on the jet algorithm used to cluster additional radiation.…”

“…The algorithm presented in refs. [37,38] to calculate weights for jet events at NLO accuracy modifies the recombination procedure used to cluster two primary objects into a resulting jet. It is thus possible to keep the kinematics Born-like, leading to a straightforward identification of real and virtual contributions without any further restrictions on the variables chosen to describe the event.…”