EPJ

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EPJ A - Hadrons and Nuclei
Hadrons and Nuclei


Eur. Phys. J. A 14, 113-124 (2002)
DOI: 10.1140/epja/iepja1373

Role of $\mth{\Delta}$ exchange for $\mth{p \bar p}$ annihilation into two-pion and three-pion channels

M. Betz1, E.A. Veit1 and J. Haidenbauer2

1  Instituto de Física - Universidade Federal do Rio Grande do Sul, Cx. P. 15051; CEP 91501-970, Porto Alegre, Brazil
2  Institut für Kernphysik, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany

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(Received: 16 January 2002 Communicated by V.V. Anisovich)

Abstract
$\mth{p \bar p}$ annihilation into two pions and three pions is studied in a baryon exchange model. Annihilation diagrams involving nucleon as well as $\Delta$-resonance exchanges are included consistently in the two- and three-pion channels. Effects from the initial-state interaction are fully taken into account. A comparison of the influence of the $\Delta$ exchange on the considered annihilation channels is made and reveals that its importance for three-pion annihilation is strongly reduced as compared to two-pion annihilation. It is found that annihilation into three uncorrelated pions can yield up to 10% of the total experimentally observed three-pion annihilation cross-section.

PACS
13.75.Cs - Nucleon-nucleon interactions (including antinucleons, deuterons, etc.).
14.20.-c - Baryons (including antiparticles).
21.30.Cb - Nuclear forces in vacuum.
25.43.+t - Antiproton-induced reactions.

© Società Italiana di Fisica, Springer-Verlag 2002

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