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The current PDF4LHC recommendation to estimate uncertainties due to parton distribution functions (PDFs) in theoretical predictions for LHC processes involves the combination of separate predictions computed using PDF sets from different…

High Energy Physics - Phenomenology · Physics 2015-09-30 Stefano Carrazza , Jose I. Latorre , Juan Rojo , Graeme Watt

We review basic ideas and recent developments on the determination of the parton substructure of the nucleon, in view of applications to precision hadron collider physics. We review the way information on parton distributions (PDFs) is…

High Energy Physics - Phenomenology · Physics 2015-03-17 Stefano Forte

An important limitation in current fits of parton distribution functions (PDFs) is that PDF uncertainties do not include any source of theoretical uncertainty. Here we present a general method for incorporating theoretical uncertainties…

High Energy Physics - Phenomenology · Physics 2018-10-05 R. L. Pearson , C. Voisey

We apply the Lagrange Multiplier method to study the uncertainties of physical predictions due to the uncertainties of parton distribution functions (PDFs), using the cross section for W production at a hadron collider as an archetypal…

High Energy Physics - Phenomenology · Physics 2009-09-25 D. Stump , J. Pumplin , R. Brock , D. Casey , J. Huston , J. Kalk , H. L. Lai , W. K. Tung

A determination of Parton Distribution Functions (PDFs) from a global fit to a dataset including measurements from the LHC has been performed. The determinations have been carried out according to the NNPDF methodology, leading to a fit…

High Energy Physics - Phenomenology · Physics 2014-11-04 Nathan Hartland

Evaluating parton density systematic uncertainties in Monte~Carlo event generator predictions has long been achieved by reweighting between the original and systematic PDFs for the initial state configurations of the individual simulated…

High Energy Physics - Phenomenology · Physics 2016-03-08 Andy Buckley

We present a method developed by the NNPDF Collaboration that allows the inclusion of new experimental data into an existing set of parton distribution functions without the need for a complete refit. A Monte Carlo ensemble of PDFs may be…

High Energy Physics - Phenomenology · Physics 2015-06-03 Francesco Cerutti , Nathan Hartland

Global QCD analyses of nuclear parton distribution functions (nPDFs) have traditionally relied on the Hessian method for uncertainty estimation. However, the inherent Gaussian approximation and reliance on local curvature often prove…

High Energy Physics - Phenomenology · Physics 2026-03-16 N. Derakhshanian , P. Risse , T. Jezo , M. Klasen , K. Kovarik , A. Kusina

In global PDF analyses, parton distribution functions (PDFs) are parametrised at a fixed input scale $Q_0$ and evolved to higher scales using the DGLAP equations. Since QCD evolution is fully determined within perturbation theory, the…

High Energy Physics - Phenomenology · Physics 2025-11-13 Ivan A. Godino , Eva D. Z. Groenendijk , Tanjona R. Rabemananjara

A selection of the latest and most frequently used parton distribution functions (PDFs) is incorporated in Pythia8, including the Monte Carlo-adapted PDFs from the MSTW and CTEQ collaborations. This article examines the differences in PDFs…

High Energy Physics - Phenomenology · Physics 2010-11-19 Tomas Kasemets , Torbjörn Sjöstrand

We examine the dependence of parton distribution functions (PDFs) on the value of the QCD coupling strength $\alpha_{s}(M_{Z})$. We explain a simple method that is rigorously valid in the quadratic approximation normally applied in PDF…

High Energy Physics - Phenomenology · Physics 2014-11-20 Hung-Liang Lai , Joey Huston , Zhao Li , Pavel Nadolsky , Jon Pumplin , Daniel Stump , C. -P. Yuan

We include uncertainties due to missing higher order corrections to QCD computations (MHOU) used in the determination of parton distributions (PDFs) in the recent NNPDF4.0 set of PDFs. We use our previously published methodology, based on…

We present a determination of the parton distributions of the nucleon from a global set of hard scattering data using the NNPDF methodology at LO and NNLO in perturbative QCD, thereby generalizing to these orders the NNPDF2.1 NLO parton…

This manuscript outlines a software package that facilitates working with probability distributions by means of Monte-Carlo methods, in a way that allows for propagation of multivariate probability distributions through arbitrary functions.…

Mathematical Software · Computer Science 2020-01-22 Fredrik Bagge Carlson

We present preliminary results on the determination of spin-dependent, or polarised, Parton Distribution Functions (PDFs) from all relevant inclusive polarised DIS data. The analysis is performed within the NNPDF approach, which provides a…

High Energy Physics - Phenomenology · Physics 2012-06-26 Emanuele R. Nocera , Stefano Forte , Giovanni Ridolfi , Juan Rojo

Lattice QCD offers the possibility of computing parton distributions from first principles, although not in the usual $\overline{MS}$ factorization scheme. We study in this paper the evolution of non-singlet parton distribution functions…

High Energy Physics - Lattice · Physics 2023-11-01 H. Dutrieux , J. Karpie , C. Monahan , K. Orginos , S. Zafeiropoulos

We present the first Monte Carlo based global QCD analysis of spin-averaged and spin-dependent parton distribution functions (PDFs) that includes nucleon isovector matrix elements in coordinate space from lattice QCD. We investigate the…

High Energy Physics - Phenomenology · Physics 2021-01-13 J. Bringewatt , N. Sato , W. Melnitchouk , Jian-Wei Qiu , F. Steffens , M. Constantinou

We develop a methodology for the construction of a Hessian representation of Monte Carlo sets of parton distributions, based on the use of a subset of the Monte Carlo PDF replicas as an unbiased linear basis, and of a genetic algorithm for…

High Energy Physics - Phenomenology · Physics 2015-09-02 Stefano Carrazza , Stefano Forte , Zahari Kassabov , Jose Ignacio Latorre , Juan Rojo

In many real-world engineering systems, the performance or reliability of the system is characterised by a scalar parameter. The distribution of this performance parameter is important in many uncertainty quantification problems, ranging…

Methodology · Statistics 2022-10-03 Robert Millar , Jinglai Li , Hui Li

We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The…

High Energy Physics - Phenomenology · Physics 2016-04-13 Nobuo Sato , W. Melnitchouk , S. E. Kuhn , J. J. Ethier , A. Accardi