6,903 research outputs found

    The chirally-odd twist-3 distribution e(x)

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    Properties of the nucleon twist-3 distribution function e(x) are reviewed. It is emphasized that the QCD equations of motion imply the existence of a delta-function at x=0 in e(x), which gives rise to the pion-nucleon sigma-term. According to the resulting ``practical'' DIS sum rules the first and the second moment of e(x) vanish, a situation analogue to that of the pure twist-3 distribution function gˉ2(x)\bar{g}_2(x).Comment: 19 pages, 3 figures, new references and figures adde

    Quantum-Hall to insulator transition

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    The crossover from the quantum Hall regime to the Hall-insulator is investigated by varying the strength of the diagonal disorder in a 2d tight-binding model. The Hall and longitudinal conductivities and the behavior of the critical states are calculated numerically. We find that with increasing disorder the current carrying states close to the band center disappear first. Simultaneously, the quantized Hall conductivity drops monotonically to zero also from higher quantized values.Comment: 5 pages LaTeX2e, 5 ps-figures included. Proceedings SemiMag13, Nijmegen 1998; to appear in Physica

    Azimuthal asymmetries and Collins analyzing power

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    Spin azimuthal asymmetries in pion electro-production in deep inelastic scattering off longitudinally polarized protons, measured by HERMES, are well reproduced theoretically with no adjustable parameters. Predictions for azimuthal asymmetries for a longitudinally polarized deuteron target are given. The z-dependence of the Collins fragmentation function is extracted. The first information on e(x) is extracted from CLAS A_LU asymmetry.Comment: 5 pages, 7 figures. Talk presented by A.V. Efremov at DIS2002, Cracow, Poland, 30 April to 4 May 2002. To appear in Acta Physica Polonica

    Transversity in Drell-Yan process of polarized protons and antiprotons in PAX experiment

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    Estimates are given for the double spin asymmetry in lepton-pair production from collisions of transversely polarized protons and antiprotons for the kinematics of the recently proposed PAX experiment at GSI on the basis of predictions for the transversity distribution from the chiral quark soliton model.Comment: 4 pages, 2 eps-figures, style files. To be published in Proceedings of 16th Intern. spin physics symposium, October 10-16, Trieste, Ital
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