Interference effect between $\phi$ and $\Lambda(1520)$ production   channels in the $\gamma p \rightarrow K^+K^-p$ reaction near threshold
  The $\phi$-$\Lambda(1520)$ interference effect in the $\gamma p\to K^+K^-p$ reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between $\phi$ and $\Lambda(1520)$ production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when $K^+K^-$ pairs are observed at forward angles, but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the $\sqrt{s}=2.1$ GeV bump structure in forward differential cross sections for $\phi$ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange and rescattering processes via other hyperon states. 
S. Y. Ryu, J. K. Ahn, T. Nakano, D. S. Ahn, S. Ajimura, H. Akimune, Y.   Asano, W. C. Chang, J. Y. Chen, S. Date, H. Ejiri, ...
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