EFFECT OF A PION-PION SCATTERING RESONANCE ON LOW ENERGY MESON- PHOTOPRODUCTION
The influence of the two- and three-pion intermediate states in the channel gamma + pi yields N + N - bar on photoproduction was studied. Application of the Cini-Fubini version of the Mandelstam representation to the amplitude H/sup (0)/ (isoscalar photen) permittsd the evaluation of the contnibution of a J = I = 1 pion-pion resonance in terms of the isovector nucleon form factors and of the quantities describing the gamma + pi yields pi + pi amplitude. In the limit of a very narrow resonance the result can be obtained by introducing an isovector vector boson coupled to gamma + pi and to N + N - bar. This contribution can be merely added to the previous evaluations of H/sup (0)/, since rescattering corrections are negligible at low energies. Argumente are given to show that the only important threepion state is a resonant I = 0, J = I state which is crudely described by an isoscalar vector beson. Some of the parameters entering in this caleulation can be obtained from experimental information on the isoscalar nucleon form factors. Though the three-pion contribution to H/sup (+)/ (isovector photon) is very simple, the final result is obtained in a more complicated way because rescattering corrections are important. Through crossing, H/sup (-)/ (isovector photon) is also affected. It seems that one of the most interesting quantities to consider, in order to compare theory and experiment, is the d sigma /sup +//d sigma /sup -/ ratio and its dependence on energies and angles. (auth)
- Research Organization:
- European Organization for Nuclear Research, Geneva
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-15-011962
- OSTI ID:
- 4070809
- Journal Information:
- Nuovo Cimento (Italy) Divided into Nuovo Cimento A and Nuovo Cimento B, Journal Name: Nuovo Cimento (Italy) Divided into Nuovo Cimento A and Nuovo Cimento B Vol. Vol: (10), 18; ISSN NUCIA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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