The Sea of Quarks and Antiquarks in the Nucleon: a Review

Abstract

The quark and gluon structure of the proton has been under intense experimental and theoretical investigation for five decades. Even for the distributions of the well-studied valence quarks, challenges such as the value of the down quark to up quark ratio at high fractional momenta remain. Much of the sea of quark-antiquark pairs emerges from the splitting of gluons and is well described by perturbative evolution in quantum chromodynamics. However, experiments confirm that there is a non-perturbative component to the sea that is not well understood and hitherto has been difficult to calculate with ab initio non-perturbative methods. This non-perturbative structure shows up, perhaps most directly, in the flavor dependence of the sea antiquark distributions. While some of the general trends can be reproduced by models, there are features of the data that do not seem to be well described. This article discusses the experimental situation, the status of calculations and models, and the directions where these studies will progress in the near future.

17 pages, 14 figures

References in corpus (19)

• New parton distributions for collider physics
• Extraction of Spin-Dependent Parton Densities and Their Uncertainties
• A first unbiased global determination of polarized PDFs and their uncertainties
• Soft-Gluon Resummation and the Valence Parton Distribution Function of the Pion
• Short Range Correlations and the EMC Effect
• A Lattice Calculation of Parton Distributions
• A complete non-perturbative renormalization prescription for quasi-PDFs
• New limits on intrinsic charm in the nucleon from global analysis of parton distributions
• Flavor Structure of the Nucleon Sea
• Kinematics of Current Region Fragmentation in Semi-Inclusive Deeply Inelastic Scattering
• Connection between the Sivers function and the anomalous magnetic moment
• Multiplicities of charged kaons from deep-inelastic muon scattering off an isoscalar target
• A Possible Resolution of the Strange Quark Polarization Puzzle ?
• Extracting the transversity distributions from single-hadron and dihadron production
• Strange quark asymmetry in the proton in chiral effective theory
• Probing the Sea Quark Content of the Proton with One-Particle-Inclusive Processes
• Nuclear effects in the proton-deuteron Drell-Yan process
• Pion-Exchange and Fermi-Motion Effects on the Proton-Deuteron Drell-Yan Process
• Sea Quark Flavor Asymmetry of Hadrons in Statistical Balance Model

Cited by in corpus (15)

• Large-Momentum Effective Theory
• The Asymmetry of Antimatter in the Proton
• Polarized Antimatter in the Proton from Global QCD Analysis
• Parton distributions of light quarks and antiquarks in the proton
• What does kinematical target mass sensitivity in DIS reveal about hadron structure?
• Light-front wave functions of mesons, baryons and pentaquarks, with topology-induced local 4-quark interaction
• Measurement of flavor asymmetry of light-quark sea in the proton with Drell-Yan dimuon production in $p+p$ and $p+d$ collisions at 120 GeV
• Strangeness content of the pion in the U(3) Nambu-Jona-Lasinio model
• Extraction of the neutron F2 structure function from inclusive proton and deuteron deep-inelastic scattering data
• Pions in Proton Structure and Everywhere Else
• Flavor asymmetry from the non-perturbative nucleon sea
• Effect of symmetry breaking of polarized light sea quarks on the nucleon and nuclear structure functions, and sum rules
• Bayesian Monte Carlo extraction of sea asymmetry with SeaQuest and STAR data
• Regarding the distribution of glue in the pion
• Non-perturbative flavor asymmetry in the nucleon and deuteron: The light-front Hamiltonian effective field theory approach