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HK: Physik der Hadronen und Kerne

HK 9: Elektromagnetische und Hadronische Sonden

HK 9.2: Talk

Monday, March 20, 2006, 17:00–17:15, G

Status of Two-Pion Production studies at CELSIUS-WASA^∗ — •F. Kren, M. Bashkanov, H. Clement, E. Doroshkevich, O. Khakimova, T. Skorodko, and G. J. Wagner — Physikalisches Institut, Universität Tübingen

Data for the ππ production in pp and pd collisions have been taken at CELSIUS using the WASA 4π detector with pellet target in the energy range from near-threshold up to 1.45 GeV. In most cases all ejectives have been detected and identified providing up to 6 kinematical overconstraints.

Wheras the near-threshold data for ppπ⁺π⁻ and ppπ⁰π⁰ channels are consistent with chiral dynamics and Roper excitation and its decay, the data for T_p > 1 GeV are dominated by the special (ΔΔ)₀₊ configuration - contrary to predictions. In addition the M_π⁰π⁰ spectrum exhibits a suprising enhancement at small masses reminiscent of Bose-Einstein correlations. Preliminary results from the nnπ⁺π⁺ channel, however, are not in favor of such a scenario. First results on the ππ isovector channels pp→dπ⁺π⁰ and pp→pnπ⁺π⁰ will be presented.

The first channels analysed in case of pd collisions are ³Heπ⁺π⁻ and ³Heπ⁰π⁰. We again find a strong enhancement at low ππ masses, in the π⁰π⁰ channel much more pronounced than in the π⁺π⁻ channel. In the final run before the shutdown of CELSIUS data for dd→⁴Heππ have been taken.

^∗ supported by BMBF (06 TU 201), DFG (Europ. Graduiertenkolleg), Landesforschungsschwerpunkt (Quasiteilchen) and EU FP6 transnational access program