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HK: Hadronen und Kerne
HK 10: Structure of Baryons, Mesons I, Crystal Barrel Results
HK 10.1: Talk
Monday, March 16, 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 (JPC=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 ± 20stat
± 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.