Nonmesonic weak decay of Λ hypernuclei within a nuclear matter formalism

Bauer, E.; Krmpoti, F

doi:10.1016/s0375-9474(03)00641-9

Cited by 20 publications

(11 citation statements)

References 64 publications

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“…The local density approximation (LDA) is employed to extend the calculation to finite nuclei. This approach was previously established [19,20] to evaluate the non-mesonic decay widths of 12 Λ C. There is a major value of this model which by itself adds sufficient novelty to the present work with respect to previous analyses [14,15] of the nucleon spectra from hypernuclear nonmesonic decay. We must indeed emphasize that the present approach is more microscopic (i.e., less phenomenological) than the previous ones.…”

Section: Models a Weak Decaymentioning

confidence: 89%

“…We have to stress that exchange terms are very important for an accurate evaluation of Γ 1 [19]. The present work calculates exactly the exchange terms in nuclear matter.…”

Section: One-nucleon Induced Decaymentioning

confidence: 97%

“…At this point we have to mention that the models of Refs. [17,19,20] have been recently improved. On the one hand, a more realistic Λ wave-function, obtained in terms of the experimental hyperon binding energy, has been considered in the LDA calculation of Refs.…”

Section: One-nucleon Induced Decaymentioning

confidence: 99%

“…With the purpose of making the extraction of Γ n /Γ p less model dependent, in the present paper we make use of an alternative framework for hypernuclear decay: it consists of a nuclear matter formalism [19,20] extended to finite nuclei via the local density approximation, with the same weak OME transition potential (containing π, ρ, K, K * , ω and η exchange) of Ref. [17], in addition to the Monte Carlo intranuclear cascade code of Ref.…”

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confidence: 99%

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Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

et al. 2010

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Recent progress has been experienced in the field of hypernuclear weak decay, especially concerning the ratio of the neutron-to proton-induced Λ nonmesonic decay rates, Γ n /Γ p . Theoretical analyses of nucleon coincidence data have been performed in a finite nucleus framework. They led to the extraction of Γ n /Γ p values in agreement with pure theoretical estimates, thus providing an evidence for the solution of a longstanding puzzle. Here we present an alternative approach to the problem, based on a nuclear matter formalism extended to finite nuclei via the local density approximation. The work is motivated by the exigence to make the determination of Γ n /Γ p from data less model dependent. One-meson-exchange potentials are used for describing both the oneand two-nucleon induced decays, ΛN → nN and ΛN N → nN N . For the latter, treated within a microscopic approach, the channels Λnn → nnn and Λpp → npp are included in addition to the mode Λnp → nnp already considered, in a phenomenological way, in previous studies. The propagation of the final nucleons in the residual nucleus is simulated by an intranuclear cascade code. We evaluate single and double coincidence nucleon spectra for the nonmesonic decay of 12 Λ C. Through the comparison of our predictions with KEK coincidence data we determine Γ n /Γ p = 0.43 ± 0.10 for this hypernucleus, confirming previous finite nucleus analyses. The use of a high nucleon kinetic energy detection threshold such as 60 MeV makes the contribution of twonucleon induced channels quite small, but final state interaction effects are still important when extracting Γ n /Γ p from measured single nucleon distributions. Coincidence spectra suffer less from these effects even for a moderate detection threshold such as 30 MeV. In any case, final state interactions have to be considered for meaningful determinations of Γ n /Γ p . 21.80.+a, 13.30.Eg, 13.75.Ev

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Section: Models a Weak Decaymentioning

confidence: 89%

“…We have to stress that exchange terms are very important for an accurate evaluation of Γ 1 [19]. The present work calculates exactly the exchange terms in nuclear matter.…”

Section: One-nucleon Induced Decaymentioning

confidence: 97%

Section: One-nucleon Induced Decaymentioning

confidence: 99%

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confidence: 99%

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Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

et al. 2010

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“…The corresponding neutroninduced transition rates n ≡ ( n → nn) were estimated through the comparison of the measured proton spectrum with that of the intranuclear cascade (INC) calculation where the n / p ratio is treated as free parameter. This procedure signalized very large experimental n/p ratios ( ∼ =0.9-2.0) [1][2][3], in comparison with theoretical estimates ( ∼ =0.3-0.5) obtained within the one-meson-exchange potential (OMEP) [4][5][6][7][8][9][10][11]. (See, for instance, Table 3 in Ref.…”

Section: Introductionmentioning

confidence: 90%

Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

et al. 2008

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We evaluate the coincidence spectra in the nonmesonic weak decay (NMWD) N → nN of hypernuclei 4 He, 5 He, 12 C, 16 O, and 28 Si, as a function of the sum of kinetic energies E nN = E n + E N for N = n, p. The strangeness-changing transition potential is described by the one-meson-exchange model, with commonly used parametrization. Two versions of the independent-particle shell model (IPSM) are employed to account for the nuclear structure of the final residual nuclei. They are as follows: (a) IPSM-a, where no correlation, except for the Pauli principle, is taken into account and (b) IPSM-b, where the highly excited hole states are considered to be quasistationary and are described by Breit-Wigner distributions, whose widths are estimated from the experimental data. All np and nn spectra exhibit a series of peaks in the energy interval 110 MeV < E nN < 170 MeV, one for each occupied shell-model state. Within the IPSM-a, and because of the recoil effect, each peak covers an energy interval proportional to A −1 , going from ∼ =4 MeV for 28 Si to ∼ =40 MeV for 4 He. Such a description could be pretty fair for the light 4 He and 5 He hypernuclei. For the remaining, heavier, hypernuclei it is very important, however, to consider as well the spreading in strength of the deep-hole states and bring into play the IPSM-b approach. Notwithstanding the nuclear model that is employed the results depend only very weakly on the details of the dynamics involved in the decay process proper. We propose that the IPSM is the appropriate lowest-order approximation for the theoretical calculations of the of kinetic energy sum spectra in the NMWD. It is in comparison to this picture that one should appraise the effects of the final-state interactions and of the two-nucleon-induced decay mode.

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Weak decay of hypernuclei —Theoretical status

Garbarino

Proceedings of the IX International Conference on Hypernuclear and Strange Particle Physics

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The physics of the weak decay of hypernuclei is briefly reviewed from a theoretical point of view. Special regard is devoted to the recent progress concerning the determination of the non-mesonic decay widths and the asymmetry parameters. While convincing evidence has been achieved for a solution of the long-standing puzzle on the ratio Γn/Γp, the discrepancies between theory and experiment on the decay asymmetries clearly highlight the exigence of dedicating further efforts in exploring new aspects of the dynamics underlying the non-mesonic weak decay.

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Nonmesonic weak decay of Λ hypernuclei within a nuclear matter formalism

Cited by 20 publications

References 64 publications

Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei

Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

Weak decay of hypernuclei —Theoretical status

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