Matching Tree-Level Matrix Elements with Interleaved Showers

Abstract

We present an implementation of the so-called CKKW-L merging scheme for combining multi-jet tree-level matrix elements with parton showers. The implementation uses the transverse-momentum-ordered shower with interleaved multiple interactions as implemented in PYTHIA8. We validate our procedure using e+e--annihilation into jets and vector boson production in hadronic collisions, with special attention to details in the algorithm which are formally sub-leading in character, but may have visible effects in some observables. We find substantial merging scale dependencies induced by the enforced rapidity ordering in the default PYTHIA8 shower. If this rapidity ordering is removed the merging scale dependence is almost negligible. We then also find that the shower does a surprisingly good job of describing the hardness of multi-jet events, as long as the hardest couple of jets are given by the matrix elements. The effects of using interleaved multiple interactions as compared to more simplistic ways of adding underlying-event effects in vector boson production are shown to be negligible except in a few sensitive observables. To illustrate the generality of our implementation, we also give some example results from di-boson production and pure QCD jet production in hadronic collisions.

44 pages, 23 figures, as published in JHEP, including all changes recommended by the referee

References in corpus (9)

• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Event generation with SHERPA 1.1
• Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions
• A standard format for Les Houches Event Files
• Interleaved Parton Showers and Tuning Prospects
• NLO matrix elements and truncated showers
• Invariant Mass Distribution of Jet Pairs Produced in Association with a W boson in ppbar Collisions at sqrt(s) = 1.96 TeV
• Multiple Jets at the LHC with High Energy Jets
• Merging parton showers and matrix elements -- back to basics

Cited by in corpus (136)

• 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
• QCD matrix elements + parton showers: The NLO case
• Merging meets matching in MC@NLO
• A critical appraisal of NLO+PS matching methods
• Dark Matter Benchmark Models for Early LHC Run-2 Searches: Report of the ATLAS/CMS Dark Matter Forum
• Search for dark matter and other new phenomena in events with an energetic jet and large missing transverse momentum using the ATLAS detector
• Merging Multi-leg NLO Matrix Elements with Parton Showers
• Searches for electroweak production of supersymmetric particles with compressed mass spectra in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Search for new phenomena in final states with an energetic jet and large missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV using the ATLAS detector
• Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report
• Soft triple-real radiation for Higgs production at N3LO
• Search for squarks and gluinos in final states with jets and missing transverse momentum using 36 fb${}^{-1}$ of $\sqrt{s}$=13 TeV $pp$ collision data with the ATLAS detector
• Search for electroweak production of supersymmetric particles in final states with two or three leptons at $\sqrt{s}=13$ TeV with the ATLAS detector
• NLO QCD matrix elements + parton showers in e+e- -> hadrons
• Search for new phenomena in events with an energetic jet and missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Drell-Yan lepton pair production at NNLO QCD with parton showers
• Search for long-lived charginos based on a disappearing-track signature in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for supersymmetry at $\sqrt{s}=13$ TeV in final states with jets and two same-sign leptons or three leptons with the ATLAS detector
• Cross-section measurements of the Higgs boson decaying into a pair of tau-leptons in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for heavy charged long-lived particles in the ATLAS detector in 36.1 fb${}^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV
• Search for electroweak production of supersymmetric states in scenarios with compressed mass spectra at $\sqrt{s}=13$ TeV with the ATLAS detector
• How low can SUSY go? Matching, monojets and compressed spectra
• Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb${}^{-1}$ of $\sqrt{s}$ =13 TeV $pp$ collision data with the ATLAS detector
• Search for chargino--neutralino pair production in final states with three leptons and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Unitarising Matrix Element + Parton Shower merging
• Controlling inclusive cross sections in parton shower + matrix element merging
• The PYTHIA Event Generator: Past, Present and Future
• Weak Gauge Boson Radiation in Parton Showers
• Search for squarks and gluinos in final states with jets and missing transverse momentum at $\sqrt{s}=$ 13 TeV with the ATLAS detector
• Search for chargino-neutralino production using recursive jigsaw reconstruction in final states with two or three charged leptons in proton-proton collisions at $\sqrt{s}$=13 TeV with the ATLAS detector
• Search for direct stau production in events with two hadronic $\tau$-leptons in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Search for invisible Higgs-boson decays in events with vector-boson fusion signatures using 139 ${\text{fb}}^{-1}$ of proton-proton data recorded by the ATLAS experiment
• Search for top squarks in final states with one isolated lepton, jets, and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Search for dark matter produced in association with bottom or top quarks in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector
• Event Generators for High-Energy Physics Experiments
• Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb${}^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data with the ATLAS detector
• Search for the direct production of charginos and neutralinos in $\sqrt{s}$ = 13 TeV $pp$ collisions with the ATLAS detector
• Search for direct top squark pair production in final states with two leptons in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• A strategy for a general search for new phenomena using data-derived signal regions and its application within the ATLAS experiment
• Search for long-lived charginos based on a disappearing-track signature using 136 fb${}^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• A practical guide to event generation for prompt photon production
• Scaling Patterns for QCD Jets
• Reinterpreting the results of the LHC with MadAnalysis 5: uncertainties and higher-luminosity estimates
• Searches for lepton-flavour-violating decays of the Higgs boson in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Search for squarks and gluinos in final states with same-sign leptons and jets using 139 fb${}^{-1}$ of data collected with the ATLAS detector
• Measuring collinear W emissions inside jets
• Exploring QCD uncertainties when setting limits on compressed SUSY spectra
• Merging NLO Multi-jet Calculations with Improved Unitarization
• Search for squarks and gluinos in events with an isolated lepton, jets, and missing transverse momentum at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• Search for gluinos in events with an isolated lepton, jets and missing transverse momentum at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• Differential cross-section measurements for the electroweak production of dijets in association with a $Z$ boson in proton-proton collisions at ATLAS
• Search for displaced vertices of oppositely charged leptons from decays of long-lived particles in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• Pulling Out All the Stops: Searching for RPV SUSY with Stop-Jets
• Automated simulations beyond the Standard Model: supersymmetry
• A Parton Shower for High Energy Jets
• Top Partner Discovery in the $T\to tZ$ channel at the LHC
• Search for new phenomena in $pp$ collisions in final states with tau leptons, $b$-jets, and missing transverse momentum with the ATLAS detector
• A search for $B-L$ $R$-parity-violating top squarks in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS experiment
• Sector Showers for Hadron Collisions
• Multi-jet merging in a variable flavor number scheme
• Probing Dark Matter with Disappearing Tracks at the LHC
• Aspects of pQCD at a 100 TeV future hadron collider
• Measurements of $W^{+}{W}^{-}+\ge 1$jet production cross-sections in $pp$ collisions at $\sqrt{s}=13$TeV with the ATLAS detector
• Sgluons in the same-sign lepton searches
• Merging weak and QCD showers with matrix elements
• Search for long-lived, massive particles in events with displaced vertices and multiple jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying into invisible particles at 13 TeV with the ATLAS detector
• Search for direct top squark pair production in events with a Higgs or $Z$ boson, and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Helicity Antenna Showers for Hadron Colliders
• Combining states without scale hierarchies with ordered parton showers
• Measurement of $b$-hadron pair production with the ATLAS detector in proton-proton collisions at $\sqrt{s}=8$ TeV
• Searches for lepton-flavour-violating decays of the Higgs boson into $e\tau$ and $\mu \tau$ in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• A study of multi-jet production in association with an electroweak vector boson
• Comparing efficient computation methods for massless QCD tree amplitudes: Closed Analytic Formulae versus Berends-Giele Recursion
• Measurement of hadronic event shapes in high-$p_{\text{T}}$ multijet final states at $\sqrt{s}=13$ TeV with the ATLAS detector
• Observation of gauge boson joint-polarisation states in $W^{\pm }Z$ production from $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Efficient multi-jet merging with the Vincia sector shower
• Search for heavy resonances decaying into a $Z$ or $W$ boson and a Higgs boson in final states with leptons and $b$-jets in $139$fb${}^{-1}$ of $pp$ collisions at $\sqrt{s}=13$TeV with the ATLAS detector
• Matching N3LO QCD calculations to parton showers
• Search for bottom-squark pair production in $pp$ collision events at $\sqrt{s}=13$ TeV with hadronically decaying $\tau$-leptons, $b$-jets and missing transverse momentum using the ATLAS detector
• Search for electroweak production of supersymmetric particles in final states with two $\tau$-leptons in $\sqrt{s}$ = 13 TeV $pp$ collisions with the ATLAS detector
• Multi-jet Merging with TMD Parton Branching
• Search for top squarks in events with a Higgs or $Z$ boson using 139 fb${}^{-1}$ of $pp$ collision data at $\sqrt{s}=13$ TeV with the ATLAS detector
• Evidence of pair production of longitudinally polarised vector bosons and study of CP properties in $ZZ\to 4\ell$ events with the ATLAS detector at $\sqrt{s}=13$ TeV
• Vector Bosons and Jets in Proton Collisions
• Measurement of the energy response of the ATLAS calorimeter to charged pions from $W^{\pm }\to {\tau }^{\pm }(\to {\pi }^{\pm }{\nu }_{\tau }){\nu }_{\tau }$ events in Run 2 data
• Search for Nearly Mass-Degenerate Higgsinos Using Low-Momentum Mildly Displaced Tracks in $pp$ Collisions at $\sqrt{s}$ = 13 TeV with the ATLAS Detector
• Flavour-violating decays of mixed top-charm squarks at the LHC
• Boosting perturbative QCD stability in quarkonium production
• Search for new phenomena in final states with two leptons and one or no $b$-tagged jets at $\sqrt{s}=13$ TeV using the ATLAS detector
• Quark jet rates and quark/gluon discrimination in multi-jet final states
• Search for dark matter produced in association with a dark Higgs boson decaying into $W^{+}{W}^{-}$ in the one-lepton final state at $\sqrt{s}$=13 TeV using 139 fb${}^{-1}$ of $pp$ collisions recorded with the ATLAS detector
• Measurements of multijet event isotropies using optimal transport with the ATLAS detector
• NLO Multijet Merging for Higgs Production Beyond the VBF Approximation
• Search for dark matter produced in association with a Higgs boson decaying to tau leptons at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for direct production of winos and higgsinos in events with two same-charge leptons or three leptons in $pp$ collision data at $\sqrt{s}=13$ TeV with the ATLAS detector
• Long Dead Winos
• Cross-section measurements for the production of a $Z$ boson in association with high-transverse-momentum jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Merging High Energy with Soft and Collinear Logarithms using HEJ and PYTHIA
• Scale and Scheme Variations in Unitarized NLO Merging
• Search for pair production of squarks or gluinos decaying via sleptons or weak bosons in final states with two same-sign or three leptons with the ATLAS detector
• Search for dark photons from Higgs boson decays via $ZH$ production with a photon plus missing transverse momentum signature from $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
• 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
• Introduction to parton-shower event generators
• Studies of Quantum Chromodynamics at the LHC
• Measurements of Lund subjet multiplicities in 13 TeV proton-proton collisions with the ATLAS detector
• Search for boosted low-mass resonances decaying into hadrons produced in association with a photon in pp collisions at $\sqrt{s}=$13 TeV with the ATLAS detector
• Measurement of the production of a $W$ boson in association with a charmed hadron in $pp$ collisions at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS detector
• A new approach to color-coherent parton evolution
• Reduce, Reuse, Reinterpret: an end-to-end pipeline for recycling particle physics results
• Study on the azimuthal angle correlation between two jets in the top quark pair production
• Semi-visible jets + X: Illuminating Dark Showers with Radiation
• Searches for direct slepton production in the compressed-mass corridor in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Constraining electroweak and strongly charged long-lived particles with CheckMATE
• Measurement of the $VH,H\to \tau \tau$ process with the ATLAS detector at 13 TeV
• Combination and Reinterpretation of LHC SUSY Searches
• Measurement of jet track functions in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for cascade decays of charged sleptons and sneutrinos in final states with three leptons and missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Optimizing pixel tracklet searches for shorter lifetimes
• Higgs production via vector-boson fusion at the LHC
• Measurement of cross-sections for production of a $Z$ boson in association with a flavor-inclusive or doubly $b$-tagged large-radius jet in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS experiment
• Search for supersymmetry in final states with missing transverse momentum and charm-tagged jets using 139 fb${}^{-1}$ of proton-proton collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector
• Search for heavy neutral leptons in decays of W bosons produced in 13 TeV pp collisions using prompt signatures in the ATLAS detector
• Implementation of full and simplified likelihoods in CheckMATE
• On the Modelling of Energetic Multi-jet QCD Events
• Measurements of $W^{+}{W}^{-}$ production cross-sections in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Test of lepton flavour universality in $W$-boson decays into electrons and $\tau$-leptons using $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for squarks and gluinos in $pp$ collisions at $\sqrt{s}=13$ TeV and $13.6$ TeV in events with $\tau$-leptons, jets and missing transverse momentum using the ATLAS detector
• Tutorial Note on Merging Matrix Elements with Parton Showers
• Vector boson plus multijet production
• A simple merging algorithm for jet angular correlation studies
• Modelling electroweak physics for the forward region
• Systematic uncertainties in NLOPS matching
• HYTREES: Combining Matrix Elements and Parton Shower for Hypothesis Testing