Non-mesonic weak decay of Λ hypernuclei within a nuclear matter framework

Abstract

The non-mesonic weak decay of Λ hypernuclei is studied using nuclear matter. We have developed a formalism which gives a microscopic interpretation of the process of emission of particles originated in this decay. More specifically, our scheme provides a unified treatment of Γ (ΛN → NN) and N N (N NN ), the Λ non-mesonic weak decay widths and the number of emitted particles (pair of particles) of kind N (NN), respectively. We have also evaluated for the first time the quantum interference terms between the n-and p-induced weak decay amplitudes. Explicit expressions for N N and N NN are shown within the ring approximation. Using the local density approximation together with the ring approximation, we report results for the decay of the 12 Λ C hypernucleus. We have obtained values for the ratio N n /N p (N nn /N np ) in the range 1.4-1.6 (0.2-0.3), where no energy threshold have been employed. The n-and p-induced interference terms modify in less than ∼ 3% these results.

Ground state normalization in the nonmesonic weak decay of 12ΛC hypernucleus within a nuclear matter formalism

“…These results are obtained by a Monte-Carlo simulation based on GEANT [26] and the INC from [3], by fitting single-proton energy spectra and using the Γ n/p -ratio as a free parameter. Let us mention that in [25] and [27], a microscopic model for the spectra itself has been developed, where the primary decays Γ n and Γ p are one ingredient within the full calculation. From this point of view, it is the nucleon emission spectra, rather than the Γ n/p -ratio, the magnitude which should be compared with data.…”

Microscopic approach to nucleon spectra in hypernuclear non-mesonic weak decay

“…A nuclear matter formalism is adopted and results for single and double-coincidence nucleon spectra are reported for 12 Λ C within the local density approximation. Previous investigations [7] demonstrated the negligible effect of ring and RPA microscopic contributions on nucleon spectra. Ground state correlations (GSC) and FSI contributions are introduced here at second order in the nucleon-nucleon interaction for the whole set of 1N and 2N isospin decay channels.…”

“…Regardless of the set of many-body contributions one considers, the Goldstone diagram technique allows us to write the total number of nucleons and nucleon pairs emitted in the non-mesonic decay as follows [7]: Note that Eqs. (1) contain five observables, N N and N N N ′ , and five unobservable decay widths, Γ N and Γ N N ′ .…”

Relationships between nonmesonic weak decays in different hypernuclei

“…The development of a microscopic many-body model for the FSI described by the INC model would be also extremely welcome, and so far only in Refs. [39,45] were the first steps taken toward this goal. Finally, the two-body induced NMWD ΛN N → nN N , which has been recently measured [15], should be also considered 2 .…”