The statistical parton distributions: status and prospects

Bourrely, Claude; Soffer, Jacques; Buccella, F.

doi:10.1140/epjc/s2005-02205-2

Cited by 147 publications

(257 citation statements)

References 44 publications

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“…The statistical model of Ref. [10] and the SU(3) version of the Chiral Quark-Soliton model of Ref. [33] both predict positive distributions, while the Meson Cloud model of Ref.…”

Section: Polarised Pdfs From a Lo Fit To The Asymmetriesmentioning

confidence: 99%

“…Unpolarised lepton scattering [2][3][4], later confirmed by DrellYan production experiments [5,6], has revealed that the light-quark difference, u − d, is negative and much larger in absolute value than expected, resulting in a large violation of the Gottfried sum rule [7]. Model calculations that explain this asymmetry also provide predictions [8][9][10] for the polarised flavour asymmetry, ∆u − ∆d.…”

Section: Introductionmentioning

confidence: 99%

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Quark helicity distributions from longitudinal spin asymmetries in muon–proton and muon–deuteron scattering

Windmolders

2010

Physics Letters B

137

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Double-spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic muon scattering have been measured by the COMPASS experiment at CERN. The data, obtained by scattering a 160 GeV muon beam off a longitudinally polarised NH 3 target, cover a range of the Bjorken variable x between 0.004 and 0.7. A leading order evaluation of the helicity distributions for the three lightest quarks and antiquark flavours derived from these asymmetries and from our previous deuteron data is presented. The resulting values of the sea quark distributions are small and do not show any sizable dependence on x in the range of the measurements. No significant difference is observed between the strange and antistrange helicity distributions, both compatible with zero. The integrated value of the flavour asymmetry of the helicity distribution of the light-quark sea, ∆u − ∆d, is found to be slightly positive, about 1.5 standard deviations away from zero.

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“…The statistical model of Ref. [10] and the SU(3) version of the Chiral Quark-Soliton model of Ref. [33] both predict positive distributions, while the Meson Cloud model of Ref.…”

Section: Polarised Pdfs From a Lo Fit To The Asymmetriesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quark helicity distributions from longitudinal spin asymmetries in muon–proton and muon–deuteron scattering

Windmolders

2010

Physics Letters B

137

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“…The QSM is therefore unbiased with respect to experimental results. A statistical model [159] which describes the nucleon as a gas of massless partons and a model based on the meson cloud picture [158].…”

Section: Resultsmentioning

confidence: 99%

Polarized Parton Distributions Measured at the HERMES Experiment

Wendland

2004

AIP Conference Proceedings

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The HERMES experiment at DESY, Germany was designed to carry out precision measurements of the proton spin structure using polarized deep-inelastic scattering. The experiment utilizes the ¾ Î electron or positron beam of the HERA accelerator which is longitudinally polarized at HERMES, in combination with a polarized internal gas target. For this work, data on longitudinally polarized hydrogen and deuterium targets were used to determine cross section asymmetries with respect to the alignment of the target and beam polarizations. Inclusive asymmetries on the proton and the deuteron, where only the scattered electron/positron is detected, were measured with high precision. In semi-inclusive deep-inelastic scattering, at least one final-state hadron is detected in coincidence. Semi-inclusive asymmetries of pions on the proton and pion and kaon asymmetries on the deuteron were measured for the first time by the HERMES collaboration. The measured asymmetries include detector effects and effects of higher-order processes in quantum electrodynamics.A new unfolding procedure that takes into account the correlations between kinematic bins was implemented to correct for these effects.The polarized parton densities of the up, down, and sea flavours were obtained from the unfolded inclusive and semi-inclusive asymmetries in a probabilistic analysis based on leading-order quantum chromodynamics. In the case of the up quark and the down quark, the polarized densities were determined to be positive and negative, respectively. The polarized densities of the sea flavours, decomposed for the first time into the densities of the anti-up, anti-down, and strange quarks, were found to be compatible with zero. Moments of the polarized parton densities were computed. TheBjørken sum rule was verified and the total spin carried by the quark spins was determined to bé ¿ ¼ ¦ ¼µ ±. This latter result is larger than earlier measurements but still smaller than ¼ ± predicted in relativistic models of the proton.iii iv ABSTRACT AcknowledgementsFirst of all I would like to thank my adviser, Dr. Michel Vetterli, for providing the opportunity to conduct research on the nucleon spin structure. His support towards the completion of this work was indispensable. I would also like to thank the members of the ¡Õ-group, notably Thore Lindemann and Marc Beckmann, whose collaboration was invaluable.My thanks go to Elke Aschenauer for her tremendous efforts in running the experiment and in contributing to the analysis. I am indebted to Naomi Makins for the numerous discussions we had.

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“…Recent measurements of multiplicities and double spin asymmetries as a function of the final transverse momentum of pions in SIDIS at JLab [8,22] suggest that transverse momentum distributions may depend on the polarization of quarks and possibly also on their flavor. Calculations of transverse momentum dependence of TMDs in different models [30][31][32][33] and on lattice [34,35] indicate that the dependence of the transverse momentum distributions on the quark polarization and flavor may be very significant.…”

Section: Introductionmentioning

confidence: 99%

Studies of the nucleon structure in back-to-back SIDIS

Avakian

2016

EPJ Web of Conferences

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Abstract. The Deep Inelastic Scattering (DIS) proved to be a great tool in testing of the theory of strong interactions, which was a major focus in last decades. Semi-Inclusive DIS (SIDIS), with detection of an additional hadron allowed first studies of 3D structure of the nucleon, moving the main focus from testing the QCD to understanding of strong interactions and quark gluon dynamics to address a number of puzzles accumulated in recent years. Detection of two hadrons in SIDIS, which is even more complicated, provides access to details of quark gluon interactions inaccessible in single-hadron SIDIS, providing a new avenue to study the complex nucleon structure. Large acceptance of the Electron Ion Collider, allowing detection of two hadrons, produced back-to-back in the current and target fragmentation regions, combined with clear separation of two regions, would provide a unique possibility to study the nucleon structure in target fragmentation region, and correlations of target and current fragmentation regions.

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The statistical parton distributions: status and prospects

Cited by 147 publications

References 44 publications

Quark helicity distributions from longitudinal spin asymmetries in muon–proton and muon–deuteron scattering

Quark helicity distributions from longitudinal spin asymmetries in muon–proton and muon–deuteron scattering

Polarized Parton Distributions Measured at the HERMES Experiment

Studies of the nucleon structure in back-to-back SIDIS

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