München 2009 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 28: QCD 2
T 28.5: Vortrag
Mittwoch, 11. März 2009, 17:45–18:00, A017
New HERMES results on spin density matrix elements from exclusive diffractive ρ0 and Φ production. — •Avetik Hayrapetyan, Michael Düren, Hasko Stenzel, Roberto Perez Benito, and Weilin Yu — Justus-Liebig Universität Gießen , Heinrich-Buff-Ring 16, 35392 Gießen
The exclusive electroproduction of vector mesons such as ρ0 and Φ in deep-inelastic scattering is of particular interest to study the production mechanism and the nucleon structure. In the HERMES experiment, angular and momentum distributions of the scattered lepton and of the vector meson decay products are measured. Recent HERMES results on Spin Density Matrix Elements (SDME) for exclusive ρ0 and Φ meson production are presented. An observed hierarchy of relative sizes of helicity amplitudes will be shown. A comparison is done for results from Hydrogen and Deuterium targets. The data indicate a small but statistically significant non-conservation of s-channel helicity for ρ0 meson production but not for Φ meson production.