Production of a neutron-rich H-6Λ hypernucleus in the Li-6(π-, K+) reaction

We study phenomenologically the production of the neutron-rich hypernucleus H-6Λ in the Li-6(π-, K+) reaction at 1.2 GeV/c, using a distorted-wave impulse approximation in a one-step mechanism, π- p → K+ Σ- via Σ- doorways caused by Σ- p ⇔ Λn coupling. The production cross section of H-6Λ(1 exc.+) is evaluated by a coupled (H-5- Λ) + (He-5-Σ-) model with a spreading potential, in comparison with the data of the missing mass spectrum at the J-PARC E10 experiment. The result indicates that the Σ- mixing probabilities in H-6Λ(1 exc.+) are PΣ-< ～ 0.2% both for sΣ state and for pΣ state in order to reproduce no significant peak in the Λ production data, so that the cross section of H-6Λ is less than on the order of 0.4 nb/sr. The sensitivity of the Σ Λ coupling and Λ potentials to the near-Λ-threshold spectrum is discussed. The shape and magnitude of the spectrum provide valuable information on the Σ Λ coupling in the production mechanism and also the nuclear structure of H-6Λ(1 exc.+).