Pion fluctuation in deep inelastic scattering

Bunyatyan, A.; Povh, Bogdan

doi:10.1140/epja/i2006-10008-x

Cited by 9 publications

(10 citation statements)

References 33 publications

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“…Figure 1 shows the values of a extracted from the flavor asymmetry as a function of n where b 2 = a 2 /n. It appears that values of a 2 are unrealistically large (a 2 > 0.4) for certain values of the flavor asymmetry and the relative fraction of Nπ/ π to be compatible with the observations in DIS [19]. Figure 2 shows that the effects of the pionic fluctuations are rather stable in their impact on G A .…”

supporting

confidence: 59%

Orbital angular momentum in the nucleon

Garvey

2010

Phys. Rev. C

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Analysis of the measured value of the integratedd-ū asymmetry (I fas = 0.147 ± 0.027) in the nucleon show it to arise from nucleon fluctuations into baryon plus pion. Requiring angular momentum conservation in these fluctuations shows the associated orbital angular momentum is equal to the value of the flavor asymmetry. DOI: 10.1103/PhysRevC.81.055212 PACS number(s): 14.20. Dh, 11.30.Hv, 14.65.Bt The partonic composition of nucleon spin has continued to occupy the attention of physicists for the past 20 years [1]. The measured asymmetry in deep inelastic lepton scattering off polarized nucleonic targets convincingly demonstrates that the summed projection of quark spins is appreciably less than the projection of the nucleon angular momentum. This short fall was in earlier times termed a "spin crisis." Currently the value of projected spin of the quarks on the total angular momentum of the proton is taken to be. Thus the projected spin carried by quarks is observed to be ∼40% of the proton's total angular momentum. Theory and experiment continue to investigate where the rest of the proton's angular momentum might reside. The most recent data suggests that the spin carried by gluons ( g) is small [2] so one must look to orbital angular momentum (OAM) carried by quarks and gluons to account for the smaller than expected angular momentum found on quark spin.The proton's total AM can be written aswith corresponding projections along the total AML q,3 is the projection of quark OAM, with the latter two terms being the projection of spin and OAM of gluons. At the present time there exists no measurement of the OAM carried by quarks or gluons. Measuring the OAM is experimentally difficult [3] but may be possible by measuring generalized parton distributions [4]. Calculation of the quark OAM has recently been carried out on the lattice [5]. In the following it will be shown shown that the OAM created in hadronic fluctuations into baryon + Goldstone boson configurations can be an important ingredient in confronting the smaller than expected value of the spin carried by quarks. The data fixing the quark spin contributions has three sources (semileptonic axial weak decays determine the following spin combinations): (i) SU(2), ( SU(2) = u − d) and (ii) SU(3) ( SU(3) = u + d − 2 s), and (iii) the asymmetry in DIS from longitudinally polarized nucleons. The approximately Q 2 = 0, axial weak decay rates of the nucleon and hyperons contain all the correlations present in those baryonic systems while the result extracted from DIS directly accesses the charge-weighted quark spins essentially free of correlations. The approach employed below invokes a model with specific correlations (pions) that quantitatively accounts for the observed properties of theū,d difference in the proton to obtain a contribution to the OAM in the nucleon.Measurement of the flavor asymmetry in the proton via muon DIS [5] showed a large violation of the Gottfried sum rule.x dxThe measured value [6] for the integral over the sea quarks is I fas = 0.176 ±...

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supporting

confidence: 59%

Orbital angular momentum in the nucleon

Garvey

2010

Phys. Rev. C

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“…(UQM1 value) is in close agreement with the experimental value 0.17 ± 0.01 determined in an analysis of forward neutron production in electron-proton collisions at 300 GeV by the H1 and ZEUS Collaborations at DESY [14,15]. The UQM2 value is somewhat higher 0.241.…”

Section: Cqm Uqm1 Uqm2supporting

confidence: 87%

Valence and sea quarks in the nucleon

Bijker¹,

Santopinto²

2015

J. Phys.: Conf. Ser.

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“…The numerical results are shown in Table 3. The UQM1 values are in good agreement with the experimental values as determined in an analysis of forward neutron production in electron-proton collisions by the H1 and ZEUS Collaborations at DESY [16,17], and in a study of the quark distribution functions measured in Drell-Yan experiments and semi-inclusive DIS experiments [18]. The UQM2 values are about 30 % higher than the UQM1 values.…”

Section: Fluctuationssupporting

confidence: 80%