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HK: Physik der Hadronen und Kerne
HK 11: Poster-Sitzung: Elektromagnetische und hadronische Proben
HK 11.5: Poster
Dienstag, 18. März 2003, 13:30–15:30, Foyer
Indications for photoproduction of η mesic 3He — •Marco Pfeiffer — II. Physikalisches Institut, Heinrich-Buff-Ring 16, 35392 Giessen
In recent years, a lot of effort has gone into the investigation of possible quasi-bound states of η mesons and nuclei - so-called η mesic nuclei. Determinations of the η-N scattering length suggest a strong attraction of the η meson and nuclei that might result in quasi-bound states even for light nuclei like 3He. However, up to now there is no solid experimental proof for such states neither for light nor for heavier nuclear systems. In the present experiment, the possible existence of an η mesic nucleus is investigated via the η photoproduction from 3He. The experiment has been carried out at the MAMI accelerator facility in Mainz with real photons up to an energy of 820 MeV using the TAPS detector system. Two decay channels of η mesic 3He have been considered and compared to each other: the decay into the coherent η channel and the competing decay into π0pX. In the latter case, the relative opening angle of the π0-proton pair is expected to be near 180∘ for the decay of an η mesic state. The excitation functions for both decay channels show a structure near √s=1485 MeV indicating the existence of a bound η-3He state. This conjecture is supported by the measured angular distributions.