Threshold Measurements of the Reaction pp->pp pi+pi- at the COSY-11 Installation


The production of mesons in fundamental reactions like the p-p scattering near threshold is an important tool to study reaction mechanism and particle interaction. The low relative momenta of the outgoing particles near threshold result in a large interaction time, which provides a sensible probe to examine final state interactions. Measurements of the pi0-production near threshold led to theories of the nucleon-nucleon interaction which have been extended by additional short range interaction terms, being in good agreement to data. In the case of the two pion production similar unexpected results might be observed, but no realistic data exist near threshold. In addition to the nucleon-nucleon and the nucleon-pion interaction the two pion production near threshold allows to study the pion-pion interaction. Therefore, threshold measurements to the two pion production are desirable.

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