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We present a novel next-to-next-to-leading order (NNLO) QCD calculation matched to parton shower for the production of a pair of $Z$ bosons decaying to four massless leptons, $p p \to \ell^+ \ell^- \ell'^+ \ell'^- + X$, at the LHC. Spin…

High Energy Physics - Phenomenology · Physics 2021-05-26 Simone Alioli , Alessandro Broggio , Alessandro Gavardi , Stefan Kallweit , Matthew A. Lim , Riccardo Nagar , Davide Napoletano

We review recent theoretical improvements of Monte Carlo event generators for top-quark pair production and decay at the LHC based on the POWHEG method. We present an event generator that implements spin correlations and off-shell effects…

High Energy Physics - Phenomenology · Physics 2018-01-22 Tomáš Ježo

We present a consistent way of combining associated weak boson radiation in hard dijet events with hard QCD radiation in Drell-Yan-like scatterings. This integrates multiple tree-level calculations with vastly different cross sections, QCD-…

High Energy Physics - Phenomenology · Physics 2016-02-17 Jesper Roy Christiansen , Stefan Prestel

We present a new Monte Carlo event generator for the production of a top-quark pair in association with a $W^\pm$ boson at hadron colliders in the POWHEG-BOX framework. We consider the next-to-leading-order QCD corrections to the $pp\to…

High Energy Physics - Phenomenology · Physics 2021-05-19 F. Febres Cordero , M. Kraus , L. Reina

We present a calculation of the next-to-leading order QCD corrections to weakino+squark production processes at hadron colliders and their implementation in the framework of the POWHEG-BOX, a tool for the matching of fixed-order…

High Energy Physics - Phenomenology · Physics 2021-12-17 Julien Baglio , Gabriele Coniglio , Barbara Jager , Michael Spira

We discuss the extension of the matrix element method (MEM) to Next-to-Leading Order (NLO) in perturbation theory. In particular we focus on the production of a Standard Model Higgs boson which decays into four leptons.

High Energy Physics - Phenomenology · Physics 2012-05-16 John M. Campbell , Walter T. Giele , Ciaran Williams

We summarize the current status and near future prospects for next-to-next-to-leading order calculations matched to parton shower based on the MiNNLO$_{\rm PS}$ method. We give a theoretical overview, illustrate selected results for $ZZ\to…

We present an implementation of $t\bar t \ell^+\ell^-$ ($\ell=e,\mu$) hadronic production at next-to-leading order in QCD matched to parton-shower event generators in the POWHEG BOX framework. The program we developed includes all…

High Energy Physics - Phenomenology · Physics 2022-07-13 Margherita Ghezzi , Barbara Jager , Santiago Lopez Portillo Chavez , Laura Reina , Doreen Wackeroth

Recent developments in QCD phenomenology have spurred on several improved approaches to Monte Carlo event generation, relative to the post--LEP state of the art. In this brief review, the emphasis is placed on approaches for 1) consistently…

High Energy Physics - Phenomenology · Physics 2009-11-11 Peter Z. Skands

We give a status report on the automation of next-to-leading order processes within the Monte Carlo event generator WHIZARD, using GoSam and OpenLoops as provider for one-loop matrix elements. To deal with divergences, WHIZARD uses…

High Energy Physics - Phenomenology · Physics 2016-12-21 J. Reuter , B. Chokoufe , A. Hoang , W. Kilian , M. Stahlhofen , T. Teubner , C. Weiss

We introduce a twiki page with collections of generated Monte Carlo event samples in proton-proton collisions at LHC energies including a heavy quark-antiquark pair in the final state. These samples are generated with the POWHEG method and…

High Energy Physics - Phenomenology · Physics 2011-11-08 M. V. Garzelli , Adam Kardos , Zoltán Trócsányi

In this short note, I introduce to essential conceptual features and main building blocks of matrix element merging algorithms, operating on fixed order calculations both at leading order and next-to-leading order. The intention is purely…

High Energy Physics - Phenomenology · Physics 2015-03-30 Thomas Rössler

We derive an improved prescription for the merging of matrix elements with parton showers, extending the CKKW approach. A flavour-dependent phase space separation criterion is proposed. We show that this new method preserves the logarithmic…

High Energy Physics - Phenomenology · Physics 2010-03-05 Stefan Hoeche , Frank Krauss , Steffen Schumann , Frank Siegert

We present an implementation of the calculation of the production of W^+W^+ plus two jets at hadron colliders, at next-to-leading order (NLO) in QCD, in the POWHEG framework, which is a method that allows the interfacing of NLO calculations…

High Energy Physics - Phenomenology · Physics 2015-05-27 Tom Melia , Paolo Nason , Raoul Rontsch , Giulia Zanderighi

We present an implementation for slepton pair production at hadron colliders in the POWHEG BOX, a framework for combining next-to-leading order QCD calculations with parton-shower Monte-Carlo programs. Our code provides a SUSY Les Houches…

High Energy Physics - Phenomenology · Physics 2015-06-11 Barbara Jager , Andreas von Manteuffel , Stephan Thier

We illustrate how the Matrix Element Method at Next-to-Leading Order (MEM@NLO) can be used to discriminate between events arising from the production of a Higgs boson, which subsequently decays to a final state consisting of…

High Energy Physics - Phenomenology · Physics 2013-04-17 John M. Campbell , R. Keith Ellis , Walter T. Giele , Ciaran Williams

After an introduction to event generators we give an overview of developments in the field of joining matrix elements with parton showers. Starting with matrix element corrections, we also discuss implementations that match LO and NLO…

High Energy Physics - Phenomenology · Physics 2007-05-23 Stefan Gieseke

In this work we present the implementation of generators for W and Z bosons in association with two jets interfaced to parton showers using the POWHEG BOX. We incorporate matrix elements from the parton-level Monte Carlo program MCFM in the…

High Energy Physics - Phenomenology · Physics 2015-06-15 John M. Campbell , R. Keith Ellis , Paolo Nason , Giulia Zanderighi

We extend the lowest-order matching of tree-level matrix elements with parton showers to give a complete description at the next higher perturbative accuracy in alpha_s at both small and large jet resolutions, which has not been achieved so…

We propose a simple scheme to start a parton-shower evolution description from a given jet configuration in $e^+ e^-$ annihilation events. This allows a convenient combination of the full angular information content of matrix elements with…

High Energy Physics - Phenomenology · Physics 2011-01-13 J. André , T. Sjöstrand