Tübingen 2003 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 28: Elektromagnetische und hadronische Proben IV
HK 28.2: Vortrag
Mittwoch, 19. März 2003, 11:15–11:30, F
Study of the a0+(980) resonance with ANKE — •P. Fedorets1, V. Kleber2, and M. Büscher2 — 1ITEP, Moscow — 2Forschungszentrum Jülich, IKP
The a0+(980) resonance, produced in pp → da0+ reactions, has been investigated via a measurement of the two main decay channels a0+ → π+η and a0+ → K0K+. The experiments have been performed with the ANKE spectrometer (COSY Jülich) at energies Tp=2.65 and 2.83 GeV. ANKE allows to detect fast forward emitted deuterons in coincidence with K+- or π+-mesons. The two a0+ decay channels have been selected by a missing mass analysis. For Tp=2.65 GeV the missing mass distribution m(pp,d) shows a narrow peak structure, limited by the K0K+ threshold (mmin=991 MeV) and the beam energy (mmax =1038 MeV). The K+K0 and dK0 invariant mass distributions as well as angular distributions allow to draw conclusions about the K+K0 (via the a0+(980) resonance) and dK0 (Λ(1405)) FSI. The total cross section for the reaction pp → K+K0 is ∼50 nb which is in excellent agreement with model calculations predicting dominance of resonant K+K0 production. The interpretation of the π+η channel is more difficult since the η peak in the m(pp,dπ+) distribution sits on a huge background of multi-pion production. Nevertheless, after background subtraction a resonant structure (Γ∼40 MeV) can be seen in the m(pp,d) distribution. At T=2.83 GeV the possible missing mass m(pp,d) range is wider than for 2.65 GeV. This opens the opportunity to determine the ratio of resonant(via the a0+)/non resonant K0K+ production. Preliminary results of the data analysis will be shown.