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Isospin Decomposition of the Photoproduced Σπ System Near the Λ(1405)

Recent experimental results for the reaction γ+ p \to K^+ + Σ+ π from CLAS at Jefferson Lab are discussed. It was found that the mass distributions or "line shapes" of the three charge combinations Σ^+ π^-, Σ^0 π^0 and Σ^- π^+ differ significantly. Our results show that the Λ(1405), as the I=0 constituent of the reaction, must be accompanied by an I > 0 component. We discuss phenomenological fits to the data to test the possible forms and magnitudes of these amplitudes. A two-amplitude I=0 fit of Breit-Wigner form to the Σ^0π^0 channel alone works quite well. The addition of a single I=1 amplitude works fairly well to model all the line shapes simultaneously.