Photon-fusion reactions from the chiral Lagrangian with dynamical light vector mesons

We study the reactions γγ→π0π0, π+π−, \(K^{0}\bar{K}^{0}\), K+K−, ηη and π0η based on a chiral Lagrangian with dynamical light vector mesons as formulated within the hadrogenesis conjecture. At present our chiral Lagrangian contains five unknown parameters that are relevant for the photon-fusion reactions. They parameterize the strength of interaction terms involving two vector meson fields. These parameters are fitted to photon-fusion data γγ→π0π0, π+π−,π0η and to the decay η→π0γγ. In order to derive gauge invariant reaction amplitudes in the resonance region constraints from maximal analyticity and exact coupled-channel unitarity are used. Our results are in good agreement with the existing experimental data from threshold up to about 0.9 GeV for the two-pion final states. The a0 meson in the π0η channel is dynamically generated and an accurate reproduction of the γγ→π0η data is achieved up to 1.2 GeV. Based on our parameter sets we predict the γγ→ \(K^{0}\bar{K}^{0}\), K+K−, ηη cross sections.