Nonmesonic weak decay of light hypernuclei with coherent Σ mixing

Abstract Nonmesonic weak decays of the A =4, and 5 hypernuclei are studied. The short range parts of the hyperon–nucleon weak interactions are described by the direct quark (DQ) weak transition potential, while the longer range interactions are given by the π and K meson exchange processes. Virtual Σ mixings of the coherent type are found to give significant effects on the decay rates of 4 Λ He. A large violation of the ΔI =1/2 rule is predicted in the J =0 transition amplitudes.