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A coupled channel model is used to study the nature of the scalar mesons produced in the decay φ → γππ. The KK molecular picture of f 0 (980) is found to be in a good agreement with the recent experimental data from SND and CMD-2. The structure of the light scalar mesons is elucidated by investigating the S-matrix poles and the qq spectral density.

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The scattering of light exotic atoms in excited states (n = 2-5) from hydrogen has been calculated in a close-coupling model. For the first time, the absorption cross sections for hadronic atoms due to Stark collisions have been calculated by taking the shifts and widths of the nS states into account in a self-consistent quantum mechanical framework. A classical-trajectory Monte Carlo method has been used to calculate the scattering of exotic atoms from molecular hydrogen for n 8. The Coulomb transitions with n > 1 are found to be the dominant deexcitation mechanism at the initial stage of the cascade.

A coupled channel model is used to study the nature of the f 0 (980) resonance. It is shown that the existence of two poles close to KK threshold, as found in many data fits and confirmed here, can be reconciled with the KK molecular origin of the f 0 (980). Due to a strong coupling between channels the number of the S-matrix poles close to the physical region in the physical case exceeds the number of bare states introduced in the model.