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

Abstract

We study the reactions γγ → π0 π0, π+ π-, K0K̄0, 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 π0 η 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 → K0 K̄0, K+ K-, ηη cross sections. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.