Merging Multi-leg NLO Matrix Elements with Parton Showers

Abstract

We discuss extensions the CKKW-L and UMEPS tree-level matrix element and parton shower merging approaches to next-to-leading order accuracy. The generalisation of CKKW-L is based on the NL3 scheme previously developed for e+e- -annihilation, which is extended to also handle hadronic collisions by a careful treatment of parton densities. NL3 is further augmented to allow for more readily accessible NLO input. To allow for a more careful handling of merging scale dependencies we introduce an extension of the UMEPS method. This approach, dubbed UNLOPS, does not inherit problematic features of CKKW-L, and thus allows for a theoretically more appealing definition of NLO merging. We have implemented both schemes in Pythia8, and present results for the merging of W- and Higgs-production events, where the zero- and one-jet contribution are corrected to next-to-leading order simultaneously, and higher jet multiplicities are described by tree-level matrix elements. The implementation of the procedure is completely general and can be used for higher jet multiplicities and other processes, subject to the availability of programs able to correctly generate the corresponding partonic states to leading and next-to-leading order accuracy.

updated references, submitted to JHEP

References in corpus (22)

• PYTHIA 6.4 Physics and Manual
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• QCD matrix elements + parton showers: The NLO case
• Merging meets matching in MC@NLO
• Reducing full one-loop amplitudes to scalar integrals at the integrand level
• A standard format for Les Houches Event Files
• NLO vector-boson production matched with shower in POWHEG
• An Automated Implementation of On-Shell Methods for One-Loop Amplitudes
• MINLO: Multi-scale improved NLO
• A Numerical Unitarity Formalism for Evaluating One-Loop Amplitudes
• On the Rational Terms of the one-loop amplitudes
• NLO QCD matrix elements + parton showers in e+e- -> hadrons
• Combining Higher-Order Resummation with Multiple NLO Calculations and Parton Showers in GENEVA
• Vector boson plus one jet production in POWHEG
• Unitarising Matrix Element + Parton Shower merging
• Extending CKKW-merging to One-Loop Matrix Elements
• Numerical NLO QCD calculations
• GenEvA (I): A new framework for event generation
• WZ production beyond NLO for high-pT observables
• GenEvA (II): A phase space generator from a reweighted parton shower
• Multiple Interactions in Pythia 8
• Combining Higher-Order Resummation with Multiple NLO Calculations and Parton Showers in the GENEVA Monte Carlo Framework

Cited by in corpus (137)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Event Generation with Sherpa 2.2
• String Formation Beyond Leading Colour
• NNLOPS simulation of Higgs boson production
• Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions using the ATLAS detector
• Merging H/W/Z + 0 and 1 jet at NLO with no merging scale: a path to parton shower + NNLO matching
• Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report
• Systematics of quark/gluon tagging
• The midpoint between dipole and parton showers
• NLO QCD+EW predictions for V+jets including off-shell vector-boson decays and multijet merging
• Drell-Yan lepton pair production at NNLO QCD with parton showers
• Combining Higher-Order Resummation with Multiple NLO Calculations and Parton Showers in GENEVA
• Drell-Yan Production at NNLL'+NNLO Matched to Parton Showers
• Higgs-boson production through gluon fusion at NNLO QCD with parton showers
• Automated Parton-Shower Variations in Pythia 8
• Next-to-Leading Order W + 5-Jet Production at the LHC
• tWH associated production at the LHC
• Update of the Binoth Les Houches Accord for a standard interface between Monte Carlo tools and one-loop programs
• Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at $\sqrt{s}$=13 TeV with the ATLAS detector
• Unitarising Matrix Element + Parton Shower merging
• Matching Fully Differential NNLO Calculations and Parton Showers
• Controlling inclusive cross sections in parton shower + matrix element merging
• The PYTHIA Event Generator: Past, Present and Future
• Search for a scalar partner of the top quark in the all-hadronic $t\bar{t}$ plus missing transverse momentum final state at $\sqrt{s}=13$ TeV with the ATLAS detector
• DijetGAN: A Generative-Adversarial Network Approach for the Simulation of QCD Dijet Events at the LHC
• Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in $\sqrt{s}=13$ TeV pp collisions with the ATLAS detector
• Weak Gauge Boson Radiation in Parton Showers
• Implementing NLO DGLAP evolution in Parton Showers
• Vincia for Hadron Colliders
• Search for direct production of electroweakinos in final states with one lepton, missing transverse momentum and a Higgs boson decaying into two $b$-jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Uncertainties in MEPS@NLO calculations of h+jets
• Precision Studies of Observables in pp->W->l nu and pp->gamma,Z->l+l- processes at the LHC
• Challenges in Monte Carlo event generator software for High-Luminosity LHC
• Next-to-leading order QCD predictions for top-quark pair production with up to two jets merged with a parton shower
• Event Generators for High-Energy Physics Experiments
• A search for pair-produced resonances in four-jet final states at $\sqrt{s}$ =13 TeV with the ATLAS detector
• Antenna Showers with One-Loop Matrix Elements
• Zero and one jet combined NLO analysis of the top quark forward-backward asymmetry
• Reweighting Parton Showers
• Parton Shower Uncertainties with Herwig 7: Benchmarks at Leading Order
• Search for bottom-squark pair production with the ATLAS detector in final states containing Higgs bosons, $b$-jets and missing transverse momentum
• Soft evolution of multi-jet final states
• Improved $(g-2{)}_{\mu }$ Measurements and Supersymmetry
• Measurement of the $t\bar{t}$ production cross-section as a function of jet multiplicity and jet transverse momentum in 7 TeV proton-proton collisions with the ATLAS detector
• Merging NLO Multi-jet Calculations with Improved Unitarization
• Search for new phenomena in events with two opposite-charge leptons, jets and missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for chargino and neutralino production in final states with a Higgs boson and missing transverse momentum at $\sqrt{s}=13$ TeV with the ATLAS detector
• PanScales parton showers for hadron collisions: formulation and fixed-order studies
• Search for new phenomena in final states with $b$-jets and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Measurement of the forward Z boson production cross-section in pp collisions at $\sqrt{s}=13$ TeV
• Search for bottom squark pair production in proton--proton collisions at $\sqrt{s}=$13 TeV with the ATLAS detector
• Search for supersymmetry in events with $b$-tagged jets and missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for direct pair production of sleptons and charginos decaying to two leptons and neutralinos with mass splittings near the $W$-boson mass in $\sqrt{s}=13$TeV $pp$ collisions with the ATLAS detector
• Search for supersymmetry in events with four or more charged leptons in $139\,\mbox{fb\(^{-1}\)}$ of $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Automatic predictions in the Georgi-Machacek model at next-to-leading order accuracy
• Search for pair production of scalar leptoquarks decaying into first- or second-generation leptons and top quarks in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• Automated simulations beyond the Standard Model: supersymmetry
• What is a parton shower?
• Search for supersymmetry in final states with charm jets and missing transverse momentum in 13 TeV $pp$ collisions with the ATLAS detector
• Hadronic Final States in DIS at NNLO QCD with Parton Showers
• Search for non-resonant Higgs boson pair production in the $bb\ell \nu \ell \nu$ final state with the ATLAS detector in $pp$ collisions at $\sqrt{s}=13$ TeV
• Triple vector boson production through Higgs-Strahlung with NLO multijet merging
• Towards NNLO+PS Matching with Sector Showers
• Search for squarks and gluinos in final states with one isolated lepton, jets, and missing transverse momentum at $\sqrt{s}=13$ TeV with the ATLAS detector
• Sector Showers for Hadron Collisions
• Multi-jet merging in a variable flavor number scheme
• Next-to-leading-logarithmic PanScales showers for Deep Inelastic Scattering and Vector Boson Fusion
• QCD and Jets at Hadron Colliders
• Aspects of pQCD at a 100 TeV future hadron collider
• Underlying event sensitive observables in Drell-Yan production using GENEVA
• Simulated NNLO for high-pT observables in vector boson + jets production at the LHC
• Extending the MINLO method
• Merging weak and QCD showers with matrix elements
• Search for top squarks decaying to tau sleptons in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• A Positive Resampler for Monte Carlo Events with Negative Weights
• Automation of electroweak corrections for LHC processes
• Combining states without scale hierarchies with ordered parton showers
• Jets and threshold summation in Deductor
• Unbinned Deep Learning Jet Substructure Measurement in High $Q^2$ ep collisions at HERA
• A study of multi-jet production in association with an electroweak vector boson
• Collinear Drop
• Efficient multi-jet merging with the Vincia sector shower
• Unbiased Elimination of Negative Weights in Monte Carlo Samples
• Reweighting Monte Carlo Predictions and Automated Fragmentation Variations in Pythia 8
• Matching N3LO QCD calculations to parton showers
• Measurement of the $k_{\mathrm{t}}$ splitting scales in $Z\to \ell \ell$ events in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector
• Multiplicative-Accumulative matching of NLO calculations with parton showers
• Weak Vector Boson Production with Many Jets at the LHC $\sqrt{s}=13$ TeV
• Multi-jet Merging with TMD Parton Branching
• Vector Bosons and Jets in Proton Collisions
• Higgs as a gluon trigger
• Spin Polarisation of $t\bar{t}\gamma \gamma$ production at NLO+PS with GoSam interfaced to MadGraph5_aMC@NLO
• Precise predictions for V+2 jet backgrounds in searches for invisible Higgs decays
• Matching and event-shape NNDL accuracy in parton showers
• Boosting perturbative QCD stability in quarkonium production
• MINLO t-channel single-top plus jet
• Extrapolating W-Associated Jet-Production Ratios at the LHC
• NLO Multijet Merging for Higgs Production Beyond the VBF Approximation
• Logarithmically-accurate and positive-definite NLO shower matching
• Long Dead Winos
• Status and developments of event generators
• Investigating the Quantum Properties of Jets and the Search for a Supersymmetric Top Quark Partner with the ATLAS Detector
• Higgs and Z boson associated production via gluon fusion in the SM and the 2HDM
• Scale and Scheme Variations in Unitarized NLO Merging
• Efficient negative-weight elimination in large high-multiplicity Monte Carlo event samples
• Search for direct production of electroweakinos in final states with one lepton, jets and missing transverse momentum in pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Multi-jet physics at high-energy colliders and TMD parton evolution
• Introduction to parton-shower event generators
• Studies of Quantum Chromodynamics at the LHC
• Combining Higher-Order Resummation with Multiple NLO Calculations and Parton Showers in the GENEVA Monte Carlo Framework
• An interface between the POWHEG BOX and MadGraph5_aMC@NLO
• A search for an unexpected asymmetry in the production of $e^{+}{\mu }^{-}$ and $e^{-}{\mu }^{+}$ pairs in proton-proton collisions recorded by the ATLAS detector at $\sqrt{s}=13$ TeV
• KrkNLO matching for colour-singlet processes
• A new approach to color-coherent parton evolution
• Summary of the Topical Workshop on Top Quark Differential Distributions 2014
• Challenges for QCD theory - some personal reflections -
• The Standard Model from the LHC to future colliders: a contribution to the Workshop "What Next" of INFN
• Higgs production via vector-boson fusion at the LHC
• Automated computation of scattering amplitudes
• Soft evolution after a hard scattering process
• Sudakov evolution without unitarity
• Search for long-lived charginos and $\tau$-sleptons using final states with a disappearing track in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Reducing negative weights in Monte Carlo event generation with Sherpa
• Search for Beyond the Standard Model physics with anomaly detection in multilepton final states in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• At the Frontier of Precision QCD in the LHC Era
• Recent developments in Monte-Carlo Event Generators
• Revisiting the gluino mass limits in the pMSSM in the light of the latest LHC data and Dark Matter constraints
• Merging of matrix elements and parton showers at NLO accuracy
• Parton shower matching and merging
• Computing for Perturbative QCD - A Snowmass White Paper
• HYTREES: Combining Matrix Elements and Parton Shower for Hypothesis Testing
• Modelling electroweak physics for the forward region
• Tutorial Note on Merging Matrix Elements with Parton Showers
• Applications of higher order QCD
• Standard Model Theory for Collider Physics
• NLO calculations matched with the Nagy-Soper parton shower