Flavor and charge symmetry in the parton distributions of the nucleon

Benesh, C. J.; Londergan, J. T.

doi:10.1103/physrevc.58.1218

Cited by 14 publications

(40 citation statements)

References 25 publications

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“…This is consistent with the treatment in previous experiments [1][2][3][4] and global fits [13][14][15]. The possibility that charge symmetry could be significantly violated (CSV) at the parton level has been discussed by several authors [30][31][32][33][34][35][36] and an extensive review was recently published [36].…”

Section: Charge Symmetry and Shadowingsupporting

confidence: 75%

“…In contrast, a study [35] of sea quark CSV showed it to be roughly a factor of 10 smaller than CSV for valence quarks. This was called into question in an analysis by Boros et al [37,38] of the F 2 structure functions determined from muon and neutrino deep inelastic scattering, which concluded thatd n (x) ≈ 1.25ū p (x) at small x.…”

Section: Charge Symmetry and Shadowingmentioning

confidence: 92%

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Improved measurement of thed¯/ūasymmetry in the nucleon sea

et al. 2001

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Measurements of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on liquid hydrogen and deuterium targets are reported. Approximately 360,000 Drell-Yan muon pairs remained after all cuts on the data. ¿From these data, the ratio of anti-down (d) to anti-up (ū) quark distributions in the proton sea is determined over a wide range in Bjorken-x. These results confirm previous measurements by E866 and extend them to lower x. From these data, (d −ū) and (d −ū)dx are evaluated for 0.015 < x < 0.35. These results are compared with parameterizations of various parton distribution functions, models and experimental results from NA51, NMC and HERMES. 13.85.Qk; 14.20.Dh; 24.85.+p; 14.65.Bt

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Section: Charge Symmetry and Shadowingsupporting

confidence: 75%

Section: Charge Symmetry and Shadowingmentioning

confidence: 92%

Improved measurement of thed¯/ūasymmetry in the nucleon sea

et al. 2001

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“…Going beyond the results in [4,5,8,9,10] and [11] we present in Fig. 2 our estimates for the isospin violating sea distributions for δū and δd at Q 2 = 10 GeV 2 .…”

mentioning

confidence: 99%

“…The valence asymmetries δu v and δd v were estimated within the nonperturbative framework of the bag model [4,5,8,9,10] and resulted in a reduction of the above mentioned discrepancy by about 30%. It should be emphasized that these nonperturbative charge symmetry violating contributions arise predominantly through mass differences δm = m d − m u of the struck quark and from target mass corrections related to δM = M n − M p .…”

mentioning

confidence: 99%

Radiatively Generated Isospin Violations in the Nucleon and the NuTeV Anomaly

Glück

Jimenez-Delgado²,

Reya³

2005

Phys. Rev. Lett.

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Predictions of isospin asymmetries of valence and sea distributions are presented which are generated by QED leading O(α) photon bremsstrahlung effects. Together with isospin violations arising from nonperturbative hadronic sources (such as quark and target mass differences) as well as with even a conservative contribution from a strangeness asymmetry (s =s), the discrepancy between the large NuTeV 'anomaly' result for sin 2 θ W and the world average of other measurements is removed.

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“…Charge symmetry for parton distributions has been investigated recently by several groups 5,6 . We review here the work of Benesh and Londergan 6 .…”

Section: A Model For Parton Charge Symmetry Violationmentioning

confidence: 99%

Validity of flavor symmetry and charge symmetry for parton distributions

Londergan

1998

Nuclear Physics A

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Recent experimental measurements of the Gottfried Sum Rule, and pp and pD Drell-Yan processes, suggest significant violation of flavor symmetry in the proton sea. This interpretation rests on the assumption of parton charge symmetry. Our model calculations suggest charge symmetry violation [CSV] for parton valence distributions of a few percent. Precision measurements of structure functions in muon and neutrino reactions allow us to set rather stringent experimental limits on CSV in certain kinematic regions. In another region, these experiments suggest substantial CSV effects. We suggest experiments which could test parton CSV. Flavor Symmetry in Parton DistributionsThe basic features of parton distributions have been well established through measurements of deep inelastic scattering [DIS], Drell-Yan processes and direct photon experiments. Precision tests of approximate symmetries allow us to understand the details of nucleon parton distributions. For example, we know that the strange quark distribution is substantially smaller than the light nonstrange sea, due to the relatively large mass of the s quark (this is sometimes termed SU(3) flavor symmetry violation)1 . A new generation of precise high energy experiments allows us to examine finer details of parton distributions. An example of this is the NMC experiment 2 , which measured µp and µD DIS, and accurately tested the Gottfried Sum Rule S G by comparing F µp 2 and F µn 2 . Assumingd p (x) =ū p (x) one predicts S G = 1/3. pQCD predicts very small deviations from 1/3. The NMC result S G = 0.235 ± 0.026 was four standard deviations lower than the "naive" prediction, apparently indicating significant flavor symmetry violation [FSV] in the proton sea.This was followed by a comparison of pp and pD Drell-Yan [DY] processes 3 . For large x F the ratio of DY cross sections will be larger than one ifd p (x) > u p (x), as observed in the E866 experiment (for a detailed discussion see the talk by W. Melnitchouk at this conference). The most promising theoretical model to date is the "meson-cloud" picture. In these models one includes a quark "core" for the nucleon plus a "cloud" of baryon-meson Fock components, and the virtual photon scatters from any of these components. Melnitchouk showed that quantitative agreement with E866 data can be achieved with a model including nucleon, pion and ∆ components.

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Flavor and charge symmetry in the parton distributions of the nucleon

Cited by 14 publications

References 25 publications

Improved measurement of thed¯/ūasymmetry in the nucleon sea

Improved measurement of thed¯/ūasymmetry in the nucleon sea

Radiatively Generated Isospin Violations in the Nucleon and the NuTeV Anomaly

Validity of flavor symmetry and charge symmetry for parton distributions

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