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HK: Physik der Hadronen und Kerne
HK 46: Electromagnetic and Hadronic Probes VI
HK 46.1: Group Report
Thursday, March 14, 2002, 16:00–16:30, D
Exclusive Measurements of the Two-Pion Production in Proton-Proton Collis ions∗ — •J. Kress, J. Pätzold, H. Clement, E. Dorochkevitch, A. Erhardt, G.J. Wagner, and U. Weidlich — Physikalisches Institut der Universität Tübingen
After installation and commissioning of the central calorimeter at COSY-TOF
runs at Tp = 750 MeV and 800 MeV have been carried out with polarized
beam
to study the reaction p→p → ppπ+π− over a large solid
angle. Deuterons, protons and pions emerging from the pp collision in the
LH2 target are identified by the Δ E−E method, π+ particles
in
addition by the recently installed delayed pulse technique. The status of
the
data analysis of these runs is presented. Data taken previously with the
PROMICE/WASA detector at CELSIUS in the energy range Tp = 650-775 MeV
have
now been fully analyzed. The final results are discussed. Besides of the
exclusive data for the ppπ+π− channel also integral cross sections
for
the channels ppπ0π0 and pnπ+π0 have been obtained. The
exclusive data show that the pp → ppπ+π− reaction at these
energies
proceeds via σ exchange and subsequent excitation of the Roper
resonance. Its decay into Nππ is observed to be practically
exclusively
into (ππ)I=l=0 pairs, either directly by N∗→ Nσ or
via
N∗→ Δ π.
∗supported by BMBF (06 TÜ 987) and DFG (European Graduate School)