Analysts of meson-meson production

We study properties of mesons, which decay into the (ππ) nnd (KK) channels, using high-statistics (meson-meson) production data for reactions of the type πN → (ππ) N πN → (KK) N with a primary interest In the J(^PC) = 0(^++) mesons. We first investigate the properties of the S* and find that it is a normal Breit-Wigner resonance. We also present evidence for a broad elastic ππ resonance, the Σ meson. We propose forms of parametrization of the coupled channel (ππ, KK) I = 0 S wave to investigate the nature of the S*and Σ. We see that it is not possible to explain these mesons simply as (qq) states and that forces in the (qqqq) sector are also important. We analyse recent (K(^-)K ) production data and find evidence for a new I = 1, O(^++) meson, the S’(l300). This (K(^-)K ) analysis also gives evidence for the spin 4, A(_2) (1900) state, illuminates theA(_2)and g production mechanisms and determines the g → KK branching ratio. We discuss the identification of the S(970) and S’(1300) and find the most natural answer is that, besides the conventional (qq) nonet, there is a low-lying (qqqq) nonet of 0(^++) mesons. Using high-statistics (K(^+)K(^-)) production data, together with the results of the (K(^-)K ) analysis, we are able to investigate I = 0 (KP) states. We first study the resonant D wave (f,f',A(_2)). Then using I = 0 D wave as a reference wave we carry out a ππ → KK phase shift analysis.