Oset, E.Marco, E.Nacher, J. C.Oller, J. A.Peláez Sagredo, José RamónRamos, A.Toki, H.2023-06-202023-06-202000[1] S. Weinberg, Physica A96 (1979) 327; J Gasser annd H. Leutwyler, Ann. Phys. NY 158 (1984) 142; J. Gasser and H. Leutwyler, Nucl. Phys. B250 (1985) 465,517,539. [2] T. N. Truong, Phys. Rev. Lett. 66 (1988) 2526; Phys. Rev. Lett. 67 (1991) 2260; A. Dobado, M.J.Herrero and T.N. Truong, Phys. Lett. B235 (1990) 134 ; A. Dobado and J.R. Peláez, Phys. Rev. D47 4883 (1993)4883 ; Phys. Rev. D56 (1997) 3057. [3] F. Guerrero and J. A. Oller, Nucl. Phys. B 537(1999)459 [4] J.A. Oller, E. Oset and J.R. Peláez, Phys. Rev. Lett. 80 (1998) 3452; Phys. Rev. D59 (1999) 074001. [5] J. A. Oller and E. Oset, Nucl. Phys. A620(1997)438; erratum Nucl. Phys. A624(1999)407 [6] E. Oset and A. Ramos, Nucl. Phys. A635(1998)99 [7] N. Kaiser, T. Waas and W. Weise, Nucl. Phys. A612 (1997) 297 [8] J.C. Nacher, A. Parreño, E. Oset, A. Ramos, A.Hosaka and M. Oka, nucl-th/9906018 [9] J.A. Oller, E. Oset and J.R. Peláez, Preprint. [10] D.N. Tovee et al., Nucl. Phys. B33(1971)493. R.J. Nowak et al., Nucl. Phys. B139 (1978)61. [11] A.D. Martin, Nucl. Phys. B179(1981)33. [12] M. Iwasaki et al., Phys. Rev. Lett. 78(1997)3067. [13] A. Gómez Nicola and J.R. Peláez, hep-ph/9909568 [14] T. S. H. Lee, J. A. Oller, E. Oset and A. Ramos, Nucl. Phys A643(1998)402 [15] J. C. Nacher, E. Oset, H. Toki and A. Ramos, Phys. Lett. B455(1999) 55 [16] T. Nakano, Talk at KEK Tanashi Symposium on Physics of Hadrons and Nuclei, Tokyo december 1998 [17] J. C. Nacher, E. Oset, H. Toki and A. Ramos, Phys. Lett. B in print, nucl-th/9902071 [18] J.A. Oller and E. Oset, Phys. Rev. D60 (1999) 074023. [19] E. Marco, E. Oset and H. Toki, Phys. Rev. C60 (1999) 015202. [20] M.N. Achasov et al., Phys. Lett. B 440 (1998) 442. R.R. Akhmetshin et al., hep-ph/9907006. M.N. Achasov et al., Phys. Lett. B 438 (1998) 441. R.R. Akhmetshin et al., hep- ph/9907005. [21] E. Marco, S. Hirenzaki, E. Oset and H. Toki, Phys. Lett. B, in print.0146-641010.1016/S0146-6410(00)00073-9https://hdl.handle.net/20.500.14352/59877©Elsevier Science BV. Erice School on Electromagnetic Probes and the Structure of Hadrons and Nuclei (1999. Erice, Italia). This work is partly supported by DGICYT, contract number PB 96-0753By means of a coupled channel non-perturbative unitary approach, it is possible to extend the strong constrains of Chiral Perturbation Theory to higher energies. In particular, it is possible to reproduce the lowest lying resonances in mesonmeson scattering up to 1.2 GeV using the parameters of the O(p²) and O ( p^ 4 ) Chiral Lagrangian. The meson baryon sector can also be tackled along similar lines. We report on an update of these results showing some examples of photon induced reactions where the techniques have been recently applied.engjournal articlehttp://dx.doi.org/10.1016/S0146-6410(00)00073-9http://www.sciencedirect.comhttp://arxiv.org/abs/nucl-th/9911040open access51-73Perturbation-theoryOne-loopScalar mesonsForm-factorsScatteringUnitarizationLagrangiansAmplitudesChannelsSymmetryFísica-Modelos matemáticosFísica matemática