Parton Distributions in Nucleons and Nuclei

Abstract

We review the current status of Parton Distribution Function (PDF) determinations for unpolarized and longitudinally polarized protons and for unpolarized nuclei, which are probed by high-energy hadronic scattering in perturbative Quantum Chromodynamics (QCD). We present the established theoretical framework, the experimental information, and the methodological aspects inherent to any modern PDF extraction. Furthermore, we summarize the present knowledge of PDFs and discuss their limitations in both accuracy and precision relevant to advance our understanding of QCD proton substructure and pursue our quest for precision in the Standard Model and beyond. In this respect, we highlight various achievements, discuss contemporary issues in PDF analyses, and outline future directions of progress.

34 pages, 5 figures, 2 tables; invited review submitted to Annual Review of Nuclear and Particle Science, Vol.70 (2020); version accepted for publication; various references updated; improved discussion on implications for astroparticle physics

References in corpus (29)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Parton distributions for the LHC
• LHAPDF6: parton density access in the LHC precision era
• Parton distributions in the LHC era: MMHT 2014 PDFs
• A first unbiased global determination of polarized PDFs and their uncertainties
• Evidence for polarization of gluons in the proton
• Thermal Dileptons at LHC
• Heavy-Quark Kinetics in the QGP at LHC
• QCDNUM: Fast QCD Evolution and Convolution
• Parton Fragmentation Functions
• Next-to-Next-to-Leading Order Evolution of Non-Singlet Fragmentation Functions
• Precision determination of electroweak parameters and the strange content of the proton from neutrino deep-inelastic scattering
• Threshold resummation at N${}^3$LL accuracy and soft-virtual cross sections at N${}^3$LO
• New limits on intrinsic charm in the nucleon from global analysis of parton distributions
• Nuclear Parton Distributions from Lepton-Nucleus Scattering and the Impact of an Electron-Ion Collider
• aMCfast: automation of fast NLO computations for PDF fits
• Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects
• APFEL Web: a web-based application for the graphical visualization of parton distribution functions
• Measurement of longitudinal spin asymmetries for weak boson production in polarized proton-proton collisions at RHIC
• Three Loop Massive Operator Matrix Elements and Asymptotic Wilson Coefficients with Two Different Masses
• Nuclear Structure Functions at a Future Electron-Ion Collider
• New analysis concerning the strange quark polarization puzzle
• Semi-inclusive Deep-Inelastic Scattering, Parton Distributions and Fragmentation Functions at a Future Electron-Ion Collider
• Multi-Messenger Physics with the Pierre Auger Observatory
• Probing the Sea Quark Content of the Proton with One-Particle-Inclusive Processes
• The three-loop polarized pure singlet operator matrix element with two different masses
• Reference results for time-like evolution up to $\mathcal{O}({\alpha }_s^3)$
• Impact of the heavy quark matching scales in PDF fits
• Parton Distribution Uncertainties using Smoothness Prior