The nonmesonic weak decay of double-hypernuclei is studied within a microscopic diagrammatic approach. In addition to the nucleon-induced mechanism, N → nN and N N → nN N , widely studied in singlehypernuclei, additional hyperon-induced mechanisms, → n, → 0 n, and → − p, are accessible in double-hypernuclei and are investigated here. As in previous works on single-hypernuclei, we adopt a nuclear matter formalism extended to finite nuclei via the local density approximation and a one-meson exchange weak transition potential (including the ground-state pseudoscalar and vector octets mesons) supplemented by correlated and uncorrelated two-pion-exchange contributions. The weak decay rates are evaluated for hypernuclei in the region of the experimentally accessible light hypernuclei 10 Be and 13 B. Our predictions are compared with a few previous evaluations. The rate for the → n decay is dominated by K-, K * -, and η-exchange and turns out to be about 2.5% of the free decay rate, free , while the total rate for the → 0 n and → − p decays, dominated by π -exchange, amounts to about 0.25% of free . The experimental measurement of these decays would be essential for the beginning of a systematic study of the nonmesonic decay of strangeness −2 hypernuclei. This field of research could also shed light on the possible existence and nature of the H dibaryon.

The nonmesonic weak decay of Λ hypernuclei is studied within a microscopic diagrammatic approach which is extended to include the three-nucleon induced mechanism. We adopt a nuclear matter formalism which, through the local density approximation, allows us to model finite hypernuclei, a one-meson-exchange weak transition potential and a Bonn nucleon-nucleon strong potential. One-, two-and three-nucleon induced weak decay rates are predicted for 12 Λ C by including ground state correlations up to second order in the nucleon-nucleon potential and the recoil of the residual nucleus. Three-nucleon stimulated decays, ΛN N N → nN N N (N = n or p), are considered here for the first time. The obtained decay rates compare well with the latest KEK and FINUDA data. The three-nucleon induced rate turns out to be dominated by nnp-and npp-induced decays, it amounts to ∼ 7% of the total nonmesonic rate and it is ∼ 1/2 of the neutron-induced decay rate. The reduction effect of the nuclear recoil is particularly relevant for the three-nucleon induced rates (∼ 15%), less important for the two-nucleon induced rates (∼ 4%) and negligible for the one-nucleon induced rates. Given the non-negligible size of the three-nucleon induced contribution and consequently its importance in the precise determination of the complete set of decay rates, new measurements and/or experimental analysis are encouraged.

The nonmesonic weak decay of Λ hypernuclei is studied within a microscopic diagrammatic approach which is extended to include the three-nucleon induced mechanism. We adopt a nuclear matter formalism which, through the local density approximation, allows us to model finite hypernuclei, a one-meson-exchange weak transition potential and a Bonn nucleon-nucleon strong potential. One-, two-and three-nucleon induced weak decay rates are predicted for 12 Λ C by including ground state correlations up to second order in the nucleon-nucleon potential and the recoil of the residual nucleus. Three-nucleon stimulated decays, ΛN N N → nN N N (N = n or p), are considered here for the first time. The obtained decay rates compare well with the latest KEK and FINUDA data. The three-nucleon induced rate turns out to be dominated by nnp-and npp-induced decays, it amounts to ∼ 7% of the total nonmesonic rate and it is ∼ 1/2 of the neutron-induced decay rate. The reduction effect of the nuclear recoil is particularly relevant for the three-nucleon induced rates (∼ 15%), less important for the two-nucleon induced rates (∼ 4%) and negligible for the one-nucleon induced rates. Given the non-negligible size of the three-nucleon induced contribution and consequently its importance in the precise determination of the complete set of decay rates, new measurements and/or experimental analysis are encouraged. Introduction -Since the first observation of Λ hypernuclei in 1953 and the introduction of the strangeness quantum number in the same year, strange nuclei have been investigated with increasing theoretical and experimental efforts [1]. Hypernuclear physics is nowadays a mature field of research which in many aspects is located at the crossroads between particle and nuclear physics. It implies important connections with QCD [2] -consider the relevance of the production of hypernuclei and anti-hypernuclei in relativistic heavy-ion collisions and the possible extension of the usual techniques of lattice QCD, effective field theories and chiral perturbation theory to the baryon-baryon interactions in the strange sector-as well as with astrophysical processes and observables [3], where it provides important inputs to study the thermal evolution, the stability, the macroscopic properties and the composition of compact astrophysical objects, including the so-called "hyperon puzzle" in neutron stars.