Eur. Phys. J. C (2013) 73: 2358
https://doi.org/10.1140/epjc/s10052-013-2358-1

Regular Article - Theoretical Physics

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

¹ GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291, Darmstadt, Germany
² Institutionen för Fysik och Astronomi, Uppsala Universitet, Box 516, 75120, Uppsala, Sweden
³ SSC RF ITEP, Bolshaya Cheremushkinskaya 25, 117218, Moscow, Russia

^* e-mail: M.Lutz@gsi.de

Received: 7 November 2012
Revised: 20 February 2013
Published online: 12 April 2013

Abstract

We study the reactions γγ→π ⁰ π ⁰, π ⁺ π ⁻, , K ⁺ K ⁻, ηη and π ⁰ η 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→π ⁰ π ⁰, π ⁺ π ⁻,π ⁰ η and to the decay η→π ⁰ γγ. 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 a ₀ meson in the π ⁰ η channel is dynamically generated and an accurate reproduction of the γγ→π ⁰ η data is achieved up to 1.2 GeV. Based on our parameter sets we predict the γγ→ , K ⁺ K ⁻, ηη cross sections.