NLO QCD matrix elements + parton showers in e+e− → hadrons

By Thomas Gehrmann, S. Höche, F. Krauss, M. Schönherr, F. Siegert. Journal of High Energy Physics, 2012

165 citations recorded by the source corpus.

We present a new approach to combine multiple NLO parton-level calculations matched to parton showers into a single inclusive event sample. The method provides a description of hard multi-jet configurations at next-to leading order in the perturbative expansion of QCD, and it is supplemented with the all-orders resummed modelling of jet fragmentation provided by the parton shower. The formal accuracy of this technique is discussed in detail, invoking the example of electron-positron annihilation into hadrons. We focus on the effect of renormalisation scale variations in particular. Comparison with experimental data from LEP underlines that this novel formalism describes data with a theoretical accuracy that has hitherto not been achieved in standard Monte Carlo event generators.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/719ddee3489d4d0a933c8c122609e32994a1d1c5

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Nuclear and High Energy Physics

Citations in the corpus

Merging H/W/Z + 0 and 1 jet at NLO with no merging scale: a path to parton shower + NNLO matching (2012, unknown): “butions accurate at the NLO level, 3 S , and, at the same time, distributions involving the Higgs boson plus one jet accurate at order 4 S . Several collaborations have addressed this merging problem [6, 7, 8, 9, 10, 11, 12, 13]. They all typically separate the output of each component simulation (t”
Soft triple-real radiation for Higgs production at N3LO (2013, unknown): “[15–35] See, for example, refs.”
NLO QCD+EW predictions for V + jets including off-shell vector-boson decays and multijet merging (2015, methodology): “Indeed, the power counting of [54, 55] shows that inclusive MEPS predictions involve uncancelled logarithms of the generic form”
Handbook of LHC Higgs Cross Sections: 3. Higgs Properties (2013, methodology): “The SHERPA [162] predictions are calculated using the MEPS@NLO method [189, 288].”
Combining higher-order resummation with multiple NLO calculations and parton showers in GENEVA (2012, background): “However, including the fixed NLO corrections outside the fixed-order region, as is done in Sherpa’s recent NLO merging [28, 29], can actually make things worse in two respects: first, numerically this will typically force the spectrum to shift toward the fixedorder result and away from the resummed ”
Les Houches 2017: Physics at TeV Colliders Standard Model Working Group Report (2017, methodology): “SHERPA–MEPS@NLO [925, 926]: pp → bb̄+ up to 3j, merging scale QCut = 20 GeV.”
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”
Event generation with Sherpa 2.2 (2019, methodology): “t emission scale only, i.e. QME last Q cut. The well-established LO approach has been promoted to include matrix elements at NLO accuracy in QCD, called M E P S @N LO , and implemented in S HERPA in [30, 132, 133]. It combines M C @N LO matched samples of increasing jet multiplicities, separated by ”
The midpoint between dipole and parton showers (2015, unknown): “This has been demonstrated, for example, in [54,55].”
Mass effects in the Higgs-gluon coupling: boosted vs. off-shell production (2014, methodology): “Our approach generalizes the Meps@Nlo method [87, 88], now including next-to-leading order corrections in the low-energy approximation as well as the top mass dependence at leading order for all jet multiplicities considered.”
QCD matrix elements + parton showers. The NLO case (2012, methodology): “where tcut = Qcut, reproducing the expressions of [43].”
Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report (2016, methodology): “13 SHERPA MEPS@NLO We provide a multijet merged sample of Higgs boson production in gluon fusion in assiciation jets wherein the h+ 0, 1, 2, 3 jet final states are calculated at NLO accuracy [244, 275, 389, 390].”
Reweighting QCD matrix-element and parton-shower calculations (2016, methodology): “The method of choice was outlined in [22,65,66,69,70] and is historically referred to as MeNloPs.”