P-wave resonant state of the He Σ 4 hypernucleus in the He 4 ( K ? , π ? ) reaction

摘要

We theoretically investigate a possible existence of a p -wave He Σ 4 resonant state with J π = 1 ? , T ? 1 / 2 above the Σ threshold, using a coupled ( 3 N – Λ ) + ( 3 N – Σ ) model with a spreading potential. We calculate inclusive and Σ – Λ conversion π ? spectra in a He 4 ( K ? , π ? ) reaction at 1.5 GeV/ c , θ lab = 4 – 12 ° by the Green's function method in a distorted-wave impulse approximation. The pole position for the p -wave Σ resonant state in He Σ 4 is determined on the Riemann sheets in the complex E plane. The result shows that a peak of the He Σ 4 resonant state is clearly obtained in the conversion spectra above the Σ threshold, and that the angular distributions of these spectra enable extraction of the contribution of the resonant state from the π ? spectra. Effects of the Σ -nucleus potential and the interference between Λ and Σ on the spectra are also discussed.