6533b827fe1ef96bd1286e27

RESEARCH PRODUCT

Λ(1405) resonance as a superposition of two states

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Chiral unitarity models have shown the existence of two states with the same quantum numbers in the vicinity of the Λ(1405), both contributing to the final experimental invariant mass distribution. The K − p → π 0 π 0 Σ 0 reaction, discussed in detail in this work, gives maximal possible weight to the second Λ(1405) state, which is narrower and of higher energy than the nominal Λ(1405). The calculated distribution of π 0 Σ 0 states forming the Λ(1405) is in agreement with a recent experimental data, and shows a peak at 1420 MeV and a relatively narrow width of Γ = 38 MeV. In contrast, the π − p → K 0 πΣ reaction gives more weight to the pole at lower energy and with a larger width. The data of these two experiments, together with the present theoretical analysis, provides a clear experimental evidence of the two pole structure of the Λ(1405). This excludes the possibility to describe the Λ(1405) as a bound state \( \bar K \) N.