Ξ * resonances in Ξ − be interactions

In an experiment carried out in the CERN SPS hyperon beam, the diffractive dissociation of incidentΞ − hyperons into ΛK − andΞ −π+π− final states has been observed. Several resonances are seen in the final states, including the well known Ξ(1820) which appears in both channels, and the Ξ(1680) which appears as a narrow state (M=1691.1±2.7 MeV/c2, Γ<8 MeV/c2) in the ΛK− channel and possibly also in the Ξππ channel.