Hypernuclear weak decay puzzle

Barbero, César Alberto; Horvat, Daniela; Krmpotić, F.; Kuo, T.T.S.; Narančić, Zoran; Tadić, D.

doi:10.1103/physrevc.66.055209

Cited by 29 publications

(157 citation statements)

References 48 publications

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“…The novelties here, in comparison with our previous works Refs. [6][7][8], are the recoil effect and the spreading of the single-particle configurations. As will be shown in Sec.…”

Section: Kinetic Energy Sum Spectrummentioning

confidence: 99%

“…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: 99%

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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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“…The novelties here, in comparison with our previous works Refs. [6][7][8], are the recoil effect and the spreading of the single-particle configurations. As will be shown in Sec.…”

Section: Kinetic Energy Sum Spectrummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

et al. 2008

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“…(4.11), (4.13), (4.14), (4.16) and appendix from [36] for the detailed definition) and we have introduced the ratios between the center of mass matrix elements:…”

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confidence: 99%

“…, being Λ M the cutoff for the meson M [36]; and ii) initial and final short range correlations which are simulated, respectively, by means of the correlation functions…”

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Intrinsic asymmetry parameter in nonmesonic hypernuclear decay: analytical proof of the independence on hypernucleus within an independent particle shell model

Barbero

Mariano

2009

Braz. J. Phys.

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We derive general analytical expressions for the evaluation of the intrinsic asymmetry parameter in nonmesonic hypernuclear weak decay, within an independent particle shell model framework. Present formalism is valid for even-even, even-odd and odd-odd core hypernucleus. A standard strangeness-changing weak transition potential with exchange of the complete meson octet (π, η, K, ρ, ω, K * ) is assumed. Very simple analytical formulas are obtained within the s-wave approximation when we restrict to the π and π + K exchange models, providing an useful and manageable tool to understand the origin of the discrepancies between theoretical and experimental results. Numerical values for 4 Λ He, 5 Λ He, 11 Λ B, 12 Λ C, 16 Λ O, 17 Λ O and 28 Λ Si hypernuclei are exhibited. Present formalism could be used to understand why new contributions to the exchange potential allow to obtain good agreement with data, as indicated in very recent works. The necessity of a consistent inclusion of: i) different modifications of the exchange potential (two-pion exchange, a 1 meson, ∆T = 3/2 terms coming from vector mesons, etc); ii) final state interactions on primary nucleons inside the residual nucleus and also correlations between the free emitted ones; and iii) configuration mixing in the final system, is remarked.

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Nonmesonic Weak Decay Spectra of Light Hypernuclei

Krmpotić

2014

Few-Body Syst

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The nonmesonic weak decay spectra of light hypernuclei have been evaluated in a systematic way. As theoretical framework we adopt the independent particle shell model with three different one-meson-exchange transition potentials. Good agreement with data is obtained for proton and neutron kinetic energy spectra of 4 Λ He, and 5 Λ He, when the recoil effect is considered. The coincidence spectra of proton-neutron pairs are also accounted for quite reasonably, but it was not possible to reproduce the data for the neutron-neutron pair spectra. It is suggested that the π + K meson-exchange model with soft monopole form factors could be a good starting point for describing the dynamics responsible for the decays of these two hypernuclei. The 4 Λ H spectra are also presented.

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Hypernuclear weak decay puzzle

Cited by 29 publications

References 48 publications

Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei

Intrinsic asymmetry parameter in nonmesonic hypernuclear decay: analytical proof of the independence on hypernucleus within an independent particle shell model

Nonmesonic Weak Decay Spectra of Light Hypernuclei

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