Observation of the (π,π) Resonance in the Pion Production Process

概要

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Coincidence measurements among three final particles in a γ(orπ)+N→N+2π process are discussed in order to fix a (π,π) resonance energy (ω_γ). It is shown that the energy of at least one of the final pions can generally be in the (3, 3) resonance region of the π-N subsystem. Even if there is the (π,π) resonance state, it has not any large influence on a pion energy spectrum. This is the qualitative reason why the isobar model can explain the pion energy spectrum. Conversely, in order to detect the (π,π) resonance effect, the disturbance due to the π-N resonance states must be avoided. For this purpose, conditions for two types of coincidence experiments are investigated kinematically. The π-π coincidence is useful if ω_<γ^2><15μ^2 or >30μ^2, μ being the pion mass. If ω_<γ^2>>18μ^2, the π-N coincidence experiment may be more adequate rather than the π-π coincidence one. The behaviors of the differential cross section on the γ-2π process which are expected from the kinematical consideration, are checked by a model with a γ-3π vertex and by another model including both the γ-3π vertex and the (3, 3) resonance state in the static approximation.
理論物理学刊行会の論文
1962-01-25