Four-baryon pointΛN→NNinteraction for the nonmesonic weak decay of the hypernucleiΛ4H,Λ4He,Λ5He,andΛ12C

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In an effort to resolve the theoretical difficulties in explaining the total and partial decay rates and the ratio ${\ensuremath{\Gamma}}_{n}/{\ensuremath{\Gamma}}_{p},$ a four-baryon point $\ensuremath{\Lambda}\stackrel{\ensuremath{\rightarrow}}{N}\mathrm{NN}$ 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 $\ensuremath{-}0.1<~{g}_{A}<~0.3$ for the isoscalar weak current of nucleons, i.e., $p(n)\ensuremath{\rightarrow}p(n)$ transitions, the partial and the total nonmesonic decay rates ${\ensuremath{\Gamma}}_{n},$ ${\ensuremath{\Gamma}}_{p},$ and ${\ensuremath{\Gamma}}_{\mathrm{nm}}={\ensuremath{\Gamma}}_{n}+{\ensuremath{\Gamma}}_{p}$ and the ratios ${\ensuremath{\Gamma}}_{n}/{\ensuremath{\Gamma}}_{p}$ of ${}_{\ensuremath{\Lambda}}^{4}\mathrm{He},$ ${}_{\ensuremath{\Lambda}}^{5}\mathrm{He},$ and ${}_{\ensuremath{\Lambda}}^{12}\mathrm{C}$ are excellently fitted in the experimental data.