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The Λ(1405) hyperon is a well-known hyperon resonance with the mass, width and spin-parity of 1405.1+1.3-1.0 MeV/c2, 50 MeV, and 1/2-, which is located just below the KbarN threshold. There is a long-standing puzzle whether the Λ(1405) is a KbarN bound state or not.
We propose an experiment at the J-PARC K1.8BR beam line to study the Λ(1405) hyperon via the (K-,n) reaction on deuteron, where a 1 GeV/c kaon is incident on the deuteron target knocking out a neutron at the forward angle and a recoiled kaon can be scattered with a residual nucleon to form the Λ(1405).
The d(K-,n) reaction populates both the isospin states of I=0 and I=1. All the decay final states of Λ(1405), Σ-π+, Σ+π-, and Σ0π0 are identified in order to decompose the isospin amplitude in the reaction.
