A critical appraisal of NLO+PS matching methods

By S. Höche, F. Krauss, M. Schönherr, F. Siegert. 2011

451 citations recorded by the source corpus.

A bstractIn this publication, uncertainties in and differences between the MC@NLO and POWHEG methods for matching next-to-leading order QCD calculations with parton showers are discussed. Implementations of both algorithms within the event generator SHERPA and based on Catani-Seymour subtraction are employed to assess the impact on a representative selection of observables. In the case of MC@NLO a substantial simplification is achieved by using dipole subtraction terms to generate the first emission. A phase space restriction is employed, which allows to vary in a transparent way the amount of non-singular radiative corrections that are exponentiated. Effects on various observables are investigated, using the production of a Higgs boson in gluon fusion, with or without an associated jet, as a benchmark process. The case of H+jet production is presented for the first time in an NLO+PS matched simulation. Uncertainties due to scale choices and non-perturbative effects are explored in the production of W± and Z bosons in association with a jet. Corresponding results are compared to data from the Tevatron and LHC experiments.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a1cb610681c23662a9a01faa552b71c3a0d742a2

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In Nuclear and High Energy Physics

Citations in the corpus

The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations (2014, methodology): “[36], and in subsequent papers, in the context of NLO-matched simulations is constructed to have the same soft behaviour of the matrix elements (see, in particular, eq.”
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report (2014, methodology): “5 Sherpa The Sherpa event generator implements the meps@nlo [30, 369] technique to merge multiple nlops matched [29] samples of successive jet multiplicities into an inclusive calculation that retains both the NLO accuracy for every individual jet multiplicity and the parton shower’s resummation pro”
Les Houches 2017: Physics at TeV Colliders Standard Model Working Group Report (2017, methodology): “A detailed tuned comparison of these amplitude generators for the production of the 4` and 2`2ν final states (off-shell ZZ and WW production) is presented at the level of amplitudes, and in combination with the Monte Carlo integration frameworks BBMC, MoCaNLO, Munich, Sherpa and Madgraph5_aMC@NLO at”
Soft triple-real radiation for Higgs production at N3LO (2013, unknown): “[15–35] See, for example, refs.”
Event generation with Sherpa 2.2 (2019, methodology): “rsion 2.2.0 S HERPA also features an independent second shower implementation, D IRE [19, 20, 21]. For the matching of NLO QCD matrix elements with parton showers S HERPA implements the MC@NLO method [22, 23]. For NNLO QCD calculations the UN2 LO P S method [24, 25] is used. The merging of multi-jet”
Mass effects in the Higgs-gluon coupling: boosted vs. off-shell production (2014, unknown): “The only subtlety in the Sherpa implementation [98, 99] is that the actual implementation of the Mc@Nlo algorithm has been slightly changed to also include sub-leading color effects in the Sudakov form factor.”
NLO Higgs boson production plus one and two jets using the POWHEG BOX, MadGraph4 and MCFM (2012, methodology): “e- and two-jet production in gluon fusion, in the large top-quark mass limit, usingthe POWHEGmethod. While for the ﬁrst process a matched NLO+shower calculation has already appeared in the literature [16], the second one has never been performed before. We have built our generators using the POWHEG ”
NLO QCD matrix elements + parton showers in e+e− → hadrons (2012, methodology): “It is motivated by the behaviour of the underlying MC@NLO event sample in terms of S- and H-events [9, 12].”
Reweighting QCD matrix-element and parton-shower calculations (2016, methodology): “ B 1) B( B) 0n(t;t)PS(O; n+1;t): (3.14) It diers from the usual PS of eq. (3.3) with respect to the splitting kernel for the rst emission and the associated denition of the Sudakov form factor, cf. [54, 58]. However, for the purpose of reweighting, all trial emissions can be treated in the same way ”
QCD matrix elements + parton showers. The NLO case (2012, methodology): “e) The MC@NLO method of [40] is used to match each n + k-parton NLO matrix element to parton showers individually.”
The midpoint between dipole and parton showers (2015, unknown): “In the past decade, the matching of parton showers to NLO calculations [32–43] and the merging of LO [44– 53] and NLO matched results for different jet multiplicity [54–59] was in the focus of interest of the majority of a e-mail: shoeche@slac.stanford.edu Monte-Carlo developers [60].”
Robust Independent Validation of Experiment and Theory: Rivet version 3 (2019, methodology): “Rivet has been widely used in the development [2–8], validation [9–16] and tuning [17–19] of event generators for Standard Model processes, as well as in the study of parton density functions (PDFs) [20,21].”