Mesonic Contributions to the Spin and Flavor Structure of the Nucleon

Speth, J.; Thomas, A. W.

doi:10.1007/0-306-47073-x_2

Cited by 143 publications

(145 citation statements)

References 93 publications

(150 reference statements)

Supporting

Mentioning

141

Contrasting

Order By: Relevance

“…A number of theoretical explanations have been advanced to explain this effect in the context of models: pion cloud; chiral quark; chiral soliton; and instanton. As real information about this phenomenon is only available for x < ∼ 0.3 and our focus is x > ∼ 0.4, we do not discuss it further herein but refer the interested reader to (Garvey and Peng, 2001;Kumano, 1998;Speth and Thomas, 1997), and references therein and thereto.…”

Section: Drell-yan Scattering Then the Ratio Becomesmentioning

confidence: 99%

Nucleon and pion distribution functions in the valence region

2010

View full text Add to dashboard Cite

We provide an experimental and theoretical perspective on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain; namely, Bjorken-x > ∼ 0.4. This domain is key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. We focus on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the Standard Model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, we explain that an upgraded Jefferson Lab facility is well-suited to provide new data on the nucleon, while a future electron ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, J-PARC and GSI, to push into the large-x domain for both mesons and nucleons. We argue furthermore that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum field theory; and a fuller exploitation of those methods. * Electronic address: holt@anl.gov † Electronic address: cdroberts@anl.gov

show abstract

Section: Drell-yan Scattering Then the Ratio Becomesmentioning

confidence: 99%

Nucleon and pion distribution functions in the valence region

2010

View full text Add to dashboard Cite

show abstract

“…Here the Mandelstam variables s, t refer to the reaction ab → cX; and the index i labels the exchange mechanism. 2 In anticipation of large contributions from the region 1 − z ≪ 1 to the considered cross section we shall use the Regge form throughout the present paper. The large Regge parameter in this case is s/s X = 1/(1 − z) and one can write the amplitudes A ab→cX i in the form…”

Section: Inclusive Production Of Pions Nucleons and Delta Isobarmentioning

confidence: 99%

Do the E866 Drell-Yan data change our picture of the chiral structure of the nucleon?

et al. 1999

Self Cite

View full text Add to dashboard Cite

We revisit the evaluation of the pionic mechanism of theū −d-asymmetry in the proton structure function. Our analysis is based on the extended AGK unitarity relation between contributions of different mechanisms to the inclusive particle production and the total photoabsorption cross-section (i.e. the proton structure function). We reanalyze the role of isovector reggeons in inclusive production of nucleons and Delta isobars in hadronic reactions. We find rather large contribution of reggeonexchange induced production of Delta isobars. This leaves much less room for the pion-exchange induced mechanism of ∆ production and provides a constraint on the πN ∆ form factor. The production of leading pions in proton-proton collisions at ISR puts additional constraints on the πN N vertex form factors. An extension of the AGK-rules to reggeon exchange suggests a negligible contribution to the proton structure function from DIS off the exchanged ρ, a2 reggeons. All these constraints are used then to estimate the pion content of the nucleon and allow to calculate parameter-free the x-dependence ofd −ū. We discuss the violation of the Gottfried Sum Rule andd-ū asymmetry and compare to the one obtained from the E866 experiment at Fermilab. We estimate the background to the pion structure function being determined by the ZEUS and H1 collaborations at HERA from leading neutron experiments.

show abstract

“…(2.5) differs from the "Sullivan" form often used in the literature [19,20,21,22], which is obtained by taking the ∆-pole contribution, D π∆ → M 2 ∆ . In particular, it has a higher power of k ⊥ (k 6 ⊥ compared with k 2 ⊥ in Eq.…”

Section: Pion Exchange Modelsmentioning

confidence: 99%

“…Our findings suggest that we can indeed describe both HERA and E866 data within pion exchange models, if the cutoff parameters in the πNN form factors are fitted simultaneously with the pion structure function. The combined fits to both the HERA and E866 data are significantly more restrictive, with models with t-dependent form factors, such as exponential or monopole, giving the best descriptions of the combined data sets over the largest range of kinematics, up to y cut ≈ 0.3 [21,22,20].…”

Section: Future Directionmentioning

confidence: 99%

Pion structure function and SU(2) flavor asymmetry

Ji¹

2017

Proceedings of QCD Evolution 2016 — PoS(QCDEV2016)

View full text Add to dashboard Cite

We refine the computation of thed −ū flavor asymmetry in the proton sea with a complementary effort to reveal the dynamics of pion exchange in high-energy processes. In particular, we discuss the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA along with thed −ū flavor asymmetry in the proton. A detailed χ 2 analysis of the ZEUS and H1 cross sections, when combined with constraints on the pion flux from Drell-Yan data, allows regions of applicability of one-pion exchange to be delineated. The analysis disfavors several models of the pion flux used in the literature, and yields an improved extraction of the pion structure function and its uncertainties at parton momentum fractions in the pion of 4 × 10 −4 x π 0.05 at a scale of Q 2 = 10 GeV 2 . Based on the fit results, we also address a possible estimate for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments at Jefferson Lab on the deuteron with forward protons.

show abstract

Mesonic Contributions to the Spin and Flavor Structure of the Nucleon

Cited by 143 publications

References 93 publications

Nucleon and pion distribution functions in the valence region

Nucleon and pion distribution functions in the valence region

Do the E866 Drell-Yan data change our picture of the chiral structure of the nucleon?

Pion structure function and SU(2) flavor asymmetry

Contact Info

Product

Resources

About