6,951 research outputs found
The chirally-odd twist-3 distribution e(x)
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 .Comment: 19 pages, 3 figures, new references and figures adde
Quantum-Hall to insulator transition
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
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
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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