Hard photon production and matrix-element parton-shower merging

By Stefan Hoeche, Steffen Schumann, F. Siegert. 2009

154 citations recorded by the source corpus.

We present a Monte Carlo approach to prompt-photon production, where photons and QCD partons are treated democratically. The photon fragmentation function is modeled by an interleaved $\mathrm{QCD}+\mathrm{QED}$ parton shower. This known technique is improved by including higher-order real-emission matrix elements. To this end, we extend a recently proposed algorithm for merging matrix elements and truncated parton showers. We exemplify the quality of the Monte Carlo predictions by comparing them to measurements of the photon fragmentation function at LEP and to measurements of prompt photon and diphoton production from the Tevatron experiments.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5d4ae423bb05b31df7162a91e946a59a6013a335

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In Nuclear and High Energy Physics

Citations in the corpus

General-purpose event generators for LHC physics (2011, methodology): “on the same footing as QCD radiation, was implemented in Sherpa and reported in [308].”
Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report (2016, methodology): “For the rejected emissions we obtain Prej = 1− Pacc → 1− qPacc = [ 1 + (1− q) Pacc1− Pacc ] Prej , (V.16) so for each of those we need to multiply the event weight with the expression in square brackets.”
Les Houches 2017: Physics at TeV Colliders Standard Model Working Group Report (2017, methodology): “The default partonshower algorithm of SHERPA is based on the Catani–Seymour factorisation [491,961].”
Event generation with Sherpa 2.2 (2019, methodology): “One option to do so is a combined QCD ⊗ QED parton shower and related multijet merging, as proposed in [105].”
Electroweak radiative corrections for collider physics (2019, methodology): “For this reason, multi-purpose event generators typically employ QED parton showers to account for photonic radiation effects, as described in the program descriptions of Herwig [462, 463], Pythia [464], and Sherpa [465, 466] in more detail.”
Reweighting QCD matrix-element and parton-shower calculations (2016, background): “A change of PDFs f → f̃ , the strong coupling αs → α̃s and the scale prefactors entering both, i.e. kαs → k̃αs and k f → k̃ f , is equivalent to modifying the emission probability accordingly:4 Pacc → qacc Pacc, qacc ≡ α̃s(k̃αs t) αs(kαs t) f̃c′( ηc x , k̃ f t) fc′( ηc x , k f t) fc(ηc, k f t) f̃c(η”
NLO matrix elements and truncated showers (2010, methodology): “While the ME+PS methods succeed at improving the simulation of multijet events, they do not address the apparent problem that the total cross sections of the simulated inclusive samples are still of leading-order 1 The algorithm has been further extended to include QED effects [10] and multi-scale p”
NLO QCD matrix elements + parton showers in e+e− → hadrons (2012, methodology): “This leads to form factors larger than one, which cannot be interpreted in terms of no-branching probabilities and which are dealt with using a modified Sudakov veto algorithm [12, 25].”
NLO QCD+EW predictions for V + jets including off-shell vector-boson decays and multijet merging (2015, methodology): “11) by a simple QCD+QED extension of the parton shower [106] or a YFS-type soft photon resummation [107], without having to match the QED part to NLO QCD+QED matrix elements.”
The midpoint between dipole and parton showers (2015, unknown): “The algorithm is equivalent to the method outlined in [74,95].”
A comprehensive approach to new physics simulations (2009, result): “It has been validated in a variety of processes [40, 77–80] and proved to yield reliable results in comparison with other generators [38, 39].”
Jet substructure at the Tevatron and LHC: new results, new tools, new benchmarksReport prepared by the participants of the BOOST 2011 Workshop at Princeton University, 22–26 May 2011. L Asquith (lasquith@hep.anl.gov), S Rappoccio (rappocc@fnal.gov) and C K Vermilion (verm@uw.edu), editors. (2011, methodology): “To accurately simulate high-pT events and to account for configurations with more than one hard parton inside a large jet, we employ sherpa’s matrix-element–partonshower matching algorithm [70, 71].”
A critical appraisal of NLO+PS matching methods (2011, methodology): “It was outlined in [29] and reformulated in [30].”