Parton distributions for LO generators

By A. Sherstnev, R. Thorne. 2007

426 citations recorded by the source corpus.

We present a study of the results obtained by combining LO partonic matrix elements with either LO or NLO parton distributions. These are compared to the best prediction using NLO for both matrix elements and parton distributions. The aim is to determine which parton distributions are most appropriate to use in those cases where only LO matrix elements are available, e.g. as in many Monte Carlo generators. Both LO and NLO parton distributions have flaws, sometimes serious, for some processes, so a modified optimal LO set is suggested. We investigate a wide variety of processes, and the new modified LO* PDF works at least as well as, and often better than, both LO and NLO PDFs in nearly all cases.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/023ee088a9133861a097a842a8a85b33a4084836

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In Nuclear and High Energy Physics

Citations in the corpus

Charged-particle multiplicities in pp interactionsmeasured with the ATLAS detector at the LHC (2010, methodology): “optimised parameters; it employs the MRST LO* parton densit y functions (PDFs) [23] and thepTordered parton shower [24].”
Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC (2012, positive): “The following parton distribution function (PDF) sets are used: CT10 [78] for the POWHEG, MC@NLO, gg2WW and gg2ZZ samples; CTEQ6L1 [79] for the PYTHIA8, ALPGEN, AcerMC, MadGraph, HERWIG and SHERPA samples; and MRSTMCal [80] for the PYTHIA6 samples.”
Measurement of the Z/ѵ* boson transverse momentum distribution in pp collisions at √s = 7 TeV with the ATLAS detector (2014, methodology): “425 with tune AUET2B and PDF set MRSTMCal [32] (referred to as Pythia6-AUET2B); Mc@nlo4.”
Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4.7 fb⁻¹ of sqrts=7 TeV proton-pro collision data (2012, positive): “Samples of simulated multijet events are generated with PYTHIA6 [22], using the MRST2007LO* modified leading-order parton distribution functions (PDFs) [23], for use in the data-driven background estimates.”
Jet reconstruction and performance using particle flow with the ATLAS Detector (2017, positive): “The minimum-bias samples are generated using Pythia 8 with the ATLAS AM2 tune [46] and the MSTW2009 PDF set [47], and are simulated using the same software as the hard-scatter event.”
Jet energy resolution in proton-proton collisions at sqrt(s) = 7 TeV recorded in 2010 with the ATLAS detector (2012, positive): “The parton distribution function (PDF) set used is the modiﬁed leading-order MRST LO* set [19].”
ATLAS search for new phenomena in dijet mass and angular distributions using pp collisions at √s=7 TeV (2012, methodology): “The QCD hard scattering interactions are simulated using the Pythia 6 [39] event generator with the ATLAS AUET2B LO** tune [40] which uses the MRSTMCal [41] modiﬁed leading-order (LO) parton distribution functions (PDFs).”
Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at $\sqrt{s}=8$ TeV with the ATLAS detector (2015, methodology): “All simulated samples are generated with a range of minimum-bias interactions (simulated using Pythia 8 with the MSTW2008LO PDF set [92] and the A2 tune [93]) overlaid on the hard-scattering event to account for the multiple pp interactions in the same bunch crossing (pile-up).”
Tuning PYTHIA 8.1: the Monash 2013 tune (2014, background): “These and other related ideas underlie recent attempts to produce modified LO PDFs such as MRST2007lomod PDFs [69] and the CT09MC1/MC2 [70] PDFs.”