Magnetic interaction induced by the anomaly in kaon-photoproductions

We study the role of magnetic interaction in the photoproduction of the kaon and hyperon. We find that the inclusion of a higher order diagram induced by the Wess-Zumio-Witten term has a significant contribution to the magnetic amplitude, which is compatible to the observed photon asymmetry in the forward angle region. This enables us to use the K coupling constants which have been determined in a microscopic way rather than the phenomenological ones which differ largely from the microscopic ones. Strangeness production is one of important subjects in hadron and nuclear physics. It is the basis of hyperon interactions and hyper-nuclear physics, where an expansion to the new dimension of strange matter is being explored. Many reactions of producing exotic states including pentaquarks are also associated with strangeness productions. Therefore, the understanding of the production mechanism is indeed a key to discuss the above interesting physics. However, the theoretical status of the production mechanism is not yet well established. Photoproduction of kaon and hyperon is one of the simplest reactions among them [1, 2, 3, 4]. If the kaon is treated as a light particle as the pion, which are altogether regarded as the NambuGoldstone bosons, their interactions are governed by the low energy theorems of chiral symmetry, respecting flavor SU(3) symmetry as well. In fact, in order to produce the kaon and hyperons, energy of order of 1 GeV must be deposited and therefore, the naive application of the low energy theorems might be doubtful. Yet, many reaction studies so far are based on the effective Lagrangian approach, the form of which is determined by symmetries compatible with flavor and chiral symmetries with much success [5, 6]. Then, various coupling constants such as kaon and vector K coupling constants are treated as parameters. In literatures, the kaon coupling constants such as gKNΛ and gKNΣ are determined microscopically from the pion coupling gπNN under flavor SU(3) symmetry rotations with suitable input of the F/D ratio [7, 8]. This method may be also applied to the K coupling constants. If we have a consistent understanding for the strong interaction, such parameters should be universal and can be applied to other reactions.