Coherent two pion photoproduction on C-12
| Autor: | S.S. Kamalov, Eulogio Oset |
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| Rok vydání: | 1997 |
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| Zdroj: | Kamalov, Sabit S. Oset Báguena, Eulogio 1997 Coherent two pion photoproduction on C-12 Nuclear Physics A 625 4 873 892 RODERIC. Repositorio Institucional de la Universitat de Valéncia instname |
| Popis: | We develop the formalism for coherent two pion photoproduction in nuclei and perform actual calculations of cross sections for $\pi^-\pi^+$ and $\pi^0\pi^0$ photoproduction on $^{12}C$. We find that due to the isospin symmetry the cross section for $\pi^0\pi^0$ production is very small and has a maximum when the pions propagate together. However, the kinematical region where the energies and polar angles of the two $\pi^0$ mesons are equal and their relative azimuthal angle $\phi=180^0$ is forbidden. Conversely in the $\pi^-\pi^+$ production the pions prefer to have a relative azimuthal angle 180$^0$ and the production of the pions propagating together is suppressed. The dominant one-body mechanism in both channels is related to the excitation of the $\Delta$ isobar. Hence the reaction can serve as a source of information about $\Delta$'s properties in nucleus. We have found that the reaction is sensitive to effects of the pion and $\Delta$ renormalization in the nuclear medium, similar to those found in the coherent $(\gamma,\pi^0)$ reaction, but magnified because of the presence of the two pions. Comment: 17 pages LATEX and 11 postscript figures |
| Databáze: | OpenAIRE |
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