Bochum 1998 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 10: Structure of Baryons, Mesons I, Crystal Barrel Results

HK 10.1: Vortrag

Montag, 16. März 1998, 14:00–14:15, H

Evidence for an Exotic ηπ Resonance with Non-qq Quantum Numbers — •W. Dünnweber, Universität München, for the CRYSTAL BARREL COLLABORATION —

The pn annihilation channel π⁻π⁰η was studied with antiprotons stopped in a liquid deuterium target, using the Crystal Barrel Detector at LEAR, CERN. The ηπ P-wave, carrying quantum numbers (J^PC=1⁻⁺) not accessible for a quark-antiquark system, is produced with a large rate (11 %). Its interferences with other resonances in this highly selective channel give evidence for resonant behaviour. A partial wave analysis yields the Breit-Wigner parameters m = 1400 ± 20_stat ± 20 _syst, Γ = 310 ± 50 +50/−30 (MeV/c²). In comparison we discuss a) indications of the same resonance found in the Russian GAMS and VES and the recent Brookhaven experiments on pion induced reactions, b) Crystal Barrel results on ηπ in other annihilation channels, and c) theoretical predictions for hybrid (qqg) and multiquark systems.