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We explore connections between two common methods for quantifying the uncertainty in parton distribution functions (PDFs), based on the Hessian error matrix and Monte-Carlo sampling. CT14 parton distributions in the Hessian representation…

High Energy Physics - Phenomenology · Physics 2017-04-05 Tie-Jiun Hou , Jun Gao , Joey Huston , Pavel Nadolsky , Carl Schmidt , Daniel Stump , Bo-Ting Wang , Ke-Ping Xie , Sayipjamal Dulat , Jon Pumplin , C. -P. Yuan

We present a set of parton distribution functions (PDFs), based on the NNPDF2.3 set, which includes a photon PDF, and QED contributions to parton evolution. We describe the implementation of the combined QCD+QED evolution in the NNPDF…

Parton distribution functions (PDFs) often include datasets corresponding to processes whereby the theoretical predictions at next-to-next-to-leading order (NNLO) in peturbative QCD have to be approximated, and this approximation may be…

High Energy Physics - Phenomenology · Physics 2024-08-21 Tanishq Sharma

The photon parton distribution function (PDF) of the proton is crucial for precise comparisons of LHC cross sections with theoretical predictions. However, it was previously affected by very large uncertainties of around ${\cal O}(100\%)$…

High Energy Physics - Phenomenology · Physics 2024-08-26 Aneesh Manohar , Paolo Nason , Gavin Salam , Giulia Zanderighi

To facilitate lattice QCD calculations of nucleon structute, a set of quasi-parton distributions were recently introduced. These quasi-PDFs were shown to reduce to standard PDFs when the nucleon is boosted to high energies, $P_z\rightarrow…

High Energy Physics - Phenomenology · Physics 2016-05-24 Leonard Gamberg , Zhong-Bo Kang , Ivan Vitev , Hongxi Xing

The current scientific standard in PDF uncertainty estimation relies either on repeated fits over artificially generated data to arrive at Monte Carlo samples of best fits or on the Hessian method, which uses a quadratic expansion of the…

High Energy Physics - Phenomenology · Physics 2024-07-23 Peter Risse , Nasim Derakhshanian , Tomas Ježo , Karol Kovařík , Aleksander Kusina

Understanding nuclear effects in parton distribution functions (PDF) is an essential component needed to determine the strange and anti-strange quark contributions in the proton. In addition Nuclear Parton Distribution Functions (NPDF) are…

High Energy Physics - Phenomenology · Physics 2010-11-19 Karol Kovarik

We review recent progress in the global determination of the collinear parton distributions (PDFs) of the proton within the NNPDF framework. This progress includes NNPDF4.0 variants with QED effects and with missing higher order…

High Energy Physics - Phenomenology · Physics 2024-06-05 Andrea Barontini , Niccolo Laurenti , Juan Rojo

I investigate the behavior of spin-dependent parton distribution functions in the regions of small and large momentum fractions $x$. I present a systematic comparison between predictions for relevant observables obtained with various models…

High Energy Physics - Phenomenology · Physics 2015-06-23 Emanuele Roberto Nocera

Global perturbative QCD analyses, based on large data sets from electron-proton and hadron collider experiments, provide tight constraints on the parton distribution function (PDF) in the proton. The extension of these analyses to nuclear…

High Energy Physics - Phenomenology · Physics 2014-11-20 Paloma Quiroga-Arias , Jose Guilherme Milhano , Urs Achin Wiedemann

We present the first unbiased determination of parton distribution functions (PDFs) with electroweak corrections. The aim of this thesis is to provide an exhaustive description of the theoretical framework and the technical implementation…

High Energy Physics - Phenomenology · Physics 2015-09-03 Stefano Carrazza

We present the next-to-next-to-leading order (NNLO) calculation of quark quasi parton distribution functions (PDFs) in the large momentum effective theory. The nontrivial factorization at this order is established explicitly and the full…

High Energy Physics - Phenomenology · Physics 2021-02-24 Long-Bin Chen , Wei Wang , Ruilin Zhu

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…

We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction…

High Energy Physics - Phenomenology · Physics 2015-10-13 Marco Bonvini , Simone Marzani , Juan Rojo , Luca Rottoli , Maria Ubiali , Richard D. Ball , Valerio Bertone , Stefano Carrazza , Nathan P. Hartland

We present a systematic comparison of theoretical predictions and various high-precision experimental measurements, specifically of differential cross sections performed by the LHC run II for Drell-Yan gauge boson, top-quark pair,…

We discuss the Bayesian approach to the solution of inverse problems and apply the formalism to analyse the closure tests performed by the NNPDF collaboration. Starting from a comparison with the approach that is currently used for the…

High Energy Physics - Phenomenology · Physics 2022-05-04 Luigi Del Debbio , Tommaso Giani , Michael Wilson

We present an investigation of the theoretical uncertainties in parton distribution functions (PDFs) due to missing higher-order corrections in the perturbative predictions used in the fit, and their relationship to the uncertainties in…

High Energy Physics - Phenomenology · Physics 2019-05-02 L. A. Harland-Lang , R. S. Thorne

We extract two nonsinglet nucleon Parton Distribution Functions from lattice QCD data for reduced Ioffe-time pseudodistributions. We perform such analysis within the NNPDF framework, considering data coming from different lattice ensembles…

High Energy Physics - Phenomenology · Physics 2021-03-17 Luigi Del Debbio , Tommaso Giani , Joseph Karpie , Kostas Orginos , Anatoly Radyushkin , Savvas Zafeiropoulos

The parton distributions functions (PDFs) derived from the NNLO QCD analysis of existing light-targets deep-inelastic-scattering data are presented. The NLO and NNLO PDFs are compared in order to analyze perturbative stability of the…

High Energy Physics - Phenomenology · Physics 2007-05-23 S. Alekhin

Beyond leading-order, perturbative QCD requires a choice of factorisation scheme to define the parton distribution functions (PDFs) and hard-process cross-section. The modified minimal-subtraction ($\overline{\mathrm{MS}}$) scheme has long…

High Energy Physics - Phenomenology · Physics 2025-05-12 Stéphane Delorme , Aleksander Kusina , Andrzej Siódmok , James Whitehead