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HK: Physik der Hadronen und Kerne

HK 12: Poster Session: Electromagentic and Hadronic Probes

HK 12.13: Poster

Dienstag, 12. März 2002, 10:30–12:45, Foyer Chemie

Azimuthal Single-Spin Asymmetries in Semi-Inklusive Deep-Inelastic Scattering — •C. Schill — Fakultät für Physik der Universität Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg.

In the HERMES experiment azimuthal single-spin asymmetries have been observed in semi-inclusive deep-inelastic scattering of 27.5 GeV electrons off a polarized hydrogen target. Azimuthal target spin asymmetries provide access to the chiral-odd spin structure function h₁(x, Q²) of the nucleon. This structure function is related to the transversity distribution δ q(x) of the quarks in the nucleon. The transversity distribution describes the probability to find a transversely polarized quark in a transversely polarized nucleon. The unpolarized quark density q(x), the longitudinally polarized quark density Δ q(x) and the transversity distribution δ q(x) together provide a complete description of the quark and spin density distributions in leading order (twist-2).

For semi-inclusively produced π⁺ and π⁰ on a hydrogen target a significant moment of sinφ is observed in the azimuthal distribution. For π⁻ the sinφ moment is found to be small. Since 1998 HERMES is taking data with a polarized deuteron target.

An investigation of the flavour dependence of the transversity distribution δ q(x) will be possible with the measurement of single-spin asymmetries for different hadrons (π⁺, π⁰, π⁻ and K⁺) and different target nucleons.

This project is supported by the German BMBF.