Observation of a narrow structure in p(gamma,K_s)X via interference with phi-meson production

We report observation of a narrow peak structure at similar to 1.54 GeV with a Gaussian width sigma = 6 MeV in the missing mass of K-S in the reaction gamma + p -> pK(S)K(L). The observed structure may be due to the interference between a strange (or antistrange) baryon resonance in the pK(L) system and the phi(KSKL) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log-likelihood ratio of the resonant signal + background hypothesis and the phi-production-based background-only hypothesis corresponds to 5.3 sigma.