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HK: Hadronen und Kerne

HK 8: Nuclear Forces I, Few Nucleon Systems

HK 8.1: Group Report

Monday, March 16, 1998, 14:00–14:30, F

Symmetries in Low Energy Pion Physics — •H. Machner and B. Razen — Institut für Kernhysik, Forschungszentrum Jülich, 52425 Jülich

The s-wave part of the π NN interaction can be related to photoproduction of pions off nucleons and to elastic pion scattering on nucleons via symmetries and four ratios. New data of the reactions pp→ π⁺d [1] and np→ π⁰d [2] close to threshold were analyzed in order to extract the s-wave part at threshold. The data were transformed via the symmetries and ratios. The results will be discussed in terms of the pion isovector scattering length. It is found that isospin is violated by 10% . The result from pp→ π⁺d reactions can be made consistent with other values for a ratio T=w(π⁻+d→ n+n+γ )/ w(π⁻+p→ n+γ ) to be 0.73± 0.06 which is 20% smaller then the accepted value.

[1] M. Drochner et al., Phys. Rev. Lett. 77, 454 (1996)

[2] D. A. Hutcheon et al., Phys. Rev. Lett. 64, 176 (1990)