Reweighting QCD matrix-element and parton-shower calculations

Bothmann, Enrico; Schönherr, Marek; Schumann, Steffen

doi:10.1140/epjc/s10052-016-4430-0

Cited by 94 publications

(87 citation statements)

References 79 publications

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“…Finally, we want to emphasize that despite the uncertainties currently present in partonshower generators [137][138][139][140], parton showers in particular (and QCD resummation techniques more generally) will be essential for understanding quark/gluon discrimination. Fixed-order QCD calculations cannot reliably probe the very soft and very collinear structure of jets, which is precisely where valuable information about quark/gluon radiation patterns reside.…”

Section: Jhep07(2017)091mentioning

confidence: 99%

Systematics of quark/gluon tagging

Gras

Höche

Kar

et al. 2017

J. High Energ. Phys.

127

164

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By measuring the substructure of a jet, one can assign it a "quark" or "gluon" tag. In the eikonal (double-logarithmic) limit, quark/gluon discrimination is determined solely by the color factor of the initiating parton (C F versus C A ). In this paper, we confront the challenges faced when going beyond this leading-order understanding, using both parton-shower generators and first-principles calculations to assess the impact of higher-order perturbative and nonperturbative physics. Working in the idealized context of electron-positron collisions, where one can define a proxy for quark and gluon jets based on the Lorentz structure of the production vertex, we find a fascinating interplay between perturbative shower effects and nonperturbative hadronization effects. Turning to protonproton collisions, we highlight a core set of measurements that would constrain current uncertainties in quark/gluon tagging and improve the overall modeling of jets at the Large Hadron Collider.

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Section: Jhep07(2017)091mentioning

confidence: 99%

Systematics of quark/gluon tagging

Gras

Höche

Kar

et al. 2017

J. High Energ. Phys.

127

164

View full text Add to dashboard Cite

show abstract

“…The dijet system with the cutp ⊥ ≥ 500 GeV as underlying hard process is typically accompanied by a large number of additional jets. Given the nature of the reweighting algorithm of [22] (and similarly for [23,44]) this may easily result in fluctuating weights. In addition we expect larger fluctuations in the nonsingular-term variations for the helicity shower, compared to the helicity-independent one.…”

Section: Example Applicationmentioning

confidence: 99%

Helicity antenna showers for hadron colliders

Fischer

Lifson

2017

Eur. Phys. J. C

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We present a complete set of helicity-dependent 2 → 3 antenna functions for QCD initial-and final-state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2 → 2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226.

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“…[31] or MadGraph [32]. Let us explain what the advantages and disadvantages are behind such a choice.…”

Section: On Reliability Of the Tauspinner Re-weighting Approachmentioning

confidence: 99%

Production of $$\tau \tau jj$$ττjj final states at the LHC and the TauSpinner algorithm: the spin-2 case

et al. 2018

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The TauSpinner algorithm is a tool that allows one to modify the physics model of the Monte Carlo generated samples due to the changed assumptions of event production dynamics, but without the need of re-generating events. With the help of weights τ -lepton production or decay processes can be modified accordingly to a new physics model. In a recent paper a new version TauSpinner ver.2.0.0 has been presented which includes a provision for introducing non-standard states and couplings and study their effects in the vector-boson-fusion processes by exploiting the spin correlations of τ -lepton pair decay products in processes where final states include also two hard jets. In the present paper we document how this can be achieved taking as an example the non-standard spin-2 state that couples to Standard Model particles and tree-level matrix elements with complete helicity information included for the parton-parton scattering amplitudes into a τ -lepton pair and two outgoing partons. This implementation is prepared as the external (user-provided) routine for the TauSpinner algorithm. It exploits amplitudes generated by MadGraph5 and adapted to the TauSpinner algorithm format. Consistency tests of the implemented matrix elements, re-weighting algorithm and numerical results for observables sensitive to τ polarisation are presented.

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Reweighting QCD matrix-element and parton-shower calculations

Cited by 94 publications

References 79 publications

Systematics of quark/gluon tagging

Systematics of quark/gluon tagging

Helicity antenna showers for hadron colliders

Production of $$\tau \tau jj$$ττjj final states at the LHC and the TauSpinner algorithm: the spin-2 case

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