Unbiased determination of polarized parton distributions and their uncertainties NNPDF Collaboration

Richard D. Ball, Stefano Forte*, Alberto Guffanti, Emanuele R. Nocera, Giovanni Ridolfi, Juan Rojo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We present a determination of a set of polarized parton distributions (PDFs) of the nucleon, at next-to-leading order, from a global set of longitudinally polarized deep-inelastic scattering data: NNPDFpoll.0. The determination is based on the NNPDF methodology: a Monte Carlo approach, with neural networks used as unbiased interpolants, previously applied to the determination of unpolarized parton distributions, and designed to provide a faithful and statistically sound representation of PDF uncertainties. We present our dataset, its statistical features, and its Monte Carlo representation. We summarize the technique used to solve the polarized evolution equations and its benchmarking, and the method used to compute physical observables. We review the NNPDF methodology for parametrization and fitting of neural networks, the algorithm used to determine the optimal fit, and its adaptation to the polarized case. We finally present our set of polarized parton distributions. We discuss its statistical properties, test for its stability upon various modifications of the fitting procedure, and compare it to other recent polarized parton sets, and in particular obtain predictions for polarized first moments of PDFs based on it. We find that the uncertainties on the gluon, and to a lesser extent the strange PDF, were substantially underestimated in previous determinations. (C) 2013 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)36-84
Number of pages49
JournalNuclear physics b
Volume874
Issue number1
DOIs
Publication statusPublished - 1 Sep 2013

Keywords

  • DEEP-INELASTIC SCATTERING
  • DEPENDENT STRUCTURE-FUNCTION
  • STRUCTURE-FUNCTION G(1)(N)
  • W LEPTON ASYMMETRY
  • BJORKEN SUM-RULE
  • SMALL-X-BEHAVIOR
  • PRECISION DETERMINATION
  • QCD ANALYSIS
  • PROTON
  • NUCLEON

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