s-wave meson-meson scattering from unitarizedU(3)chiral Lagrangians

Abstract

An investigation of the s-wave channels in meson-meson scattering is performed within a U (3) chiral unitary approach. Our calculations are based on a chiral effective Lagrangian which includes the η ′ as an explicit degree of freedom and incorporates important features of the underlying QCD Lagrangian such as the axial U (1) anomaly. We employ a coupled channel Bethe-Salpeter equation to generate poles from composed states of two pseudoscalar mesons. Our results are compared with experimental phase shifts up to 1.5 GeV and effects of the η ′ within this scheme are discussed.

Two-photon decays of $\pi^0$ , $\eta$ and $\eta'$

“…This would indicate that in the present approach some of the OZI violating corrections for F η ′ in Eq. (18) are comparable in size with the leading contribution β 2 as a free parameter is no longer possible even within the experimental error ranges. We also compare our results with the one-mixing angle scheme by putting β to the decay widths we obtain F η ′ = 1.15F π andṽ • in nice agreement with [3,4].…”

“…The usefulness of this approach lies in the fact that from a small set of parameters a large variety of data can be explained and no additional assumptions need to be made on the couplings of the resonances. In [18] the approach has been extended to include the η ′ and successfully applied to the hadronic decays of η and η ′ in [19]. The main purpose of the present work is to embed the coupled channel approach in the two-photon decays P → γ ( * ) γ ( * ) and to investigate the importance of vector-mesons for these decays from a different perspective.…”

η,η′→π+π−γ with coupled channels

“…5. The resulting T matrix describes accurately the experimental phase shifts in both the s and p wave channels [10,13]. In order to implement the non-perturbative summation of loop graphs covered by the BSE in the decay processes under consideration, we treat the BSE T matrix as an effective vertex for meson-meson scattering.…”

η, $ \eta{^\prime}$ → πl+l- in a chiral unitary approach

“…(15) which varies with the scale µ in such a way thatG mm is scale-independent [26]. After adjusting the occurring parameters the partial-wave T -matrix resulting from the BSE accurately describes the experimental phase shifts in both the s-and p-wave channels [11,27]. The implementation of non-perturbative meson-meson rescattering generated by the BSE in the amplitude A(η…”