Four-baryon point ΛN⃗NN interaction for the nonmesonic weak decay of the hypernuclei _Λ⁴H,_Λ⁴He,_Λ⁵He, and _Λ¹²C

In an effort to resolve the theoretical difficulties in explaining the total and partial decay rates and the ratio Γ_n/Γ_p, a four-baryon point ΛN⃗NN interaction is suggested as a new model for the short-range part of the nonmesonic weak decay of hypernuclei in addition to the traditional one-pion-exchange model for the long-range part. It is shown that with any value of the axial vector coupling constant g_A in the range -0.1<~g_A<~0.3 for the isoscalar weak current of nucleons, i.e., p(n)→p(n) transitions, the partial and the total nonmesonic decay rates Γ_n, Γ_p, and Γ_nm=Γ_n+Γ_p and the ratios Γ_n/Γ_p of _Λ⁴He, _Λ⁵He, and _Λ¹²C are excellently fitted in the experimental data.