Abstract
Abstract 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 C Λ 12 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, Λ N N N → n N 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.
Highlights
Since the first observation of 3 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]
Production, structure and decays are the available tools to investigate those properties of hypernuclei which in turn allow us to have access to the elementary weak and strong hyperon interactions within the flavor SU (3) sector [1]; the amount of information needed to this end would be practically impossible to obtain in scattering experiments
The first study of the three-nucleon stimulated nonmesonic weak decay of hypernuclei is presented within a microscopic approach
Summary
Since the first observation of 3 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 socalled “hyperon puzzle” in neutron stars. Most of the efforts have been devoted to the study of the nonmesonic weak decay, which from the beginning in the seventies posed important and subtle questions
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