Photoproduction of Excited Hyperons Near 1,670 MeV/c²

While the results of partial-wave analyses agree on the properties of the S = -1 hyperon resonances (S ₀₁Λ(1670), D ₀₃Λ(1690), and D ₁₃Σ(1670)), there is some disagreement between production and formation experiments in this mass region. Formation experiments observe one Σ resonance in the 1,670 MeV mass region with J ^p = 3/2^- and decaying primarily to NK̄, Λπ, and Σπ. On the other hand, production experiments have found evidence suggesting two Σ resonances in this mass region with comparable values of mass and width. Photoproduction of the hyperon resonances in the Σ(1670) region was measured from the proton in the energy from threshold to 3.0 GeV. Preliminary results from LEPS show some indication of possible different lineshapes and yields in π ^- Σ⁺ and π ⁺ Σ^- decay modes, which encourage further study in analogy of the Λ(1405).