Nuclear Structure Studied from Weak and Related Processes

Morita, Masato; Yamada, Masami; Fujita, Jun–ichi; Fujii, Akihiko; Ohtsubo, Hisao; Morita, R.; Ikeda, Kiyomi; Yokoo, Yoshimatsu; Hirooka, M.; Takahashi, Kohji

doi:10.1143/ptps.48.41

Cited by 24 publications

(9 citation statements)

References 145 publications

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“…Top Left: Predictions from the original (I) and the GT2 version (II) [149] of the Gross Theory with various Q β − values indicated by the black lines using the scale on the right-hand side (see text as for the used mass formula); Top Right: Values from [134] (denoted Staudt et al), and from [133] (denoted Moeller et al) with the modifications from [150] (crosses); Bottom Right: Predictions from the self-consistent HFB/Skyrme (QRPA) of [140], the DF/FFS (CQRPA) of [96] with the adoption of the overall quenching factor Q 2 = 0.8 and the HFB/RMF (RQRPA) of [141]; Bottom Left: A test calculation for 130 Cd [147] (denoted 86/UCRL), and the more systematic results for the N = 82 isotones [151] (noted 99/ANTOINE). The indicated values of q 2 refer to the shell-model GT quenching factor (see text) (particle-particle force) has been locally, and sometimes wildly, varied so as to reproduce the observed half-life of 130 Cd used as a renormalisation point; (4) Bottom Left: The Lanczos shell-model calculations [151] with the ANTOINE code [142] succeed in reproducing to a satisfactory level the general trend and absolute magnitudes of the known half-lives if the shell-model quenching factor (see below) q 2 = 0.55 is adopted. A former calculation performed by [147] for 130 Cd with the UCRL code [144] in a very limited model space and with a small number of iterations is inserted to illustrate the progress made in shell model calculations over the last two decades thanks to enhanced computational capabilities.…”

Section: Comparison Between Some Model Predictionsmentioning

confidence: 99%

“…The case has become even more exciting with the discovery of a Te component, referred to as Te-H, made solely of the r-isotopes 128 Te and 130 Te accompanying Xe-HL in presolar diamonds [30]. Fig.…”

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confidence: 99%

“…The two lightest and two heaviest isotopes are of pure p-and r-origin, respectively. Normalisation is to the s-only isotope 130 Xe.…”

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confidence: 99%

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The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

Arnould¹,

Goriely²,

Takahashi³

2007

Physics Reports

917

1,003

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The r-process, or the rapid neutron-capture process, of stellar nucleosynthesis is called for to explain the production of the stable (and some long-lived radioactive) neutron-rich nuclides heavier than iron that are observed in stars of various metallicities, as well as in the solar system.A very large amount of nuclear information is necessary in order to model the r-process. This concerns the static characteristics of a large variety of light to heavy nuclei between the valley of stability and the vicinity of the neutron-drip line, as well as their beta-decay branches or their reactivity. Fission probabilities of very neutron-rich actinides have also to be known in order to determine the most massive nuclei that have a chance to be involved in the r-process. Even the properties of asymmetric nuclear matter may enter the problem. The enormously challenging experimental and theoretical task imposed by all these requirements is reviewed, and the state-of-the-art development in the field is presented.Nuclear-physics-based and astrophysics-free r-process models of different levels of sophistication have been constructed over the years. We review their merits and their shortcomings. The ultimate goal of r-process studies is clearly to identify realistic sites for the development of the r-process. Here too, the challenge is enormous, and the solution still eludes us. For long, the core collapse supernova of massive stars has been envisioned as the privileged r-process location. We present a brief summary of the one-or multidimensional spherical or non-spherical explosion simulations available to-date. Their predictions are confronted with the requirements imposed to obtain an r-process. The possibility of r-nuclide synthesis during the decompression of the matter of neutron stars following their merging is also discussed.Given the uncertainties remaining on the astrophysical r-process site and on the involved nuclear physics, any confrontation between predicted r-process yields and observed abundances is clearly risky. A comparison dealing with observed r-nuclide abundances in very metal-poor stars and in the solar system is attempted on grounds of r-process models based on parametrised astrophysics conditions. The virtues of the r-process product actinides for dating old stars or the solar system are also

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Section: Comparison Between Some Model Predictionsmentioning

confidence: 99%

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The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

Arnould¹,

Goriely²,

Takahashi³

2007

Physics Reports

917

1,003

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“…Since the detailed procedure to get the explicit form of IMQ(E) 1 2 IS too much Involved to be repeated here, we omit it and only show the general "intrinsic " ing the isospin multiplet structure, 25 > and that for the Gamow-Teller transitions has a broader peak in the neighborhood of the isobaric analog state reflecting the persistence of the supermtiltiplet structure. 26 >' 10 > The two peaks seen in the strength function of the first forbidden transitions correspond to the ± hw-jumps of dipole type.…”

Section: Total Strength Of /1-decaymentioning

confidence: 99%

Application of the Gross Theory of β-Decay to Delayed Neutron Emissions

Takahashi¹

1972

Prog. Theor. Phys.

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Delayed neutron emission is investigated theoretically. First, the strength functions for the allowed and first-forbidden {.1-decays of delayed neutron precursors are calculated by the gross theory of {.1-decay developed by Takahashi, Koyama and Yamada. It is shown that the strengths obtained by the sum rule considerations of the gross theory are less energy-dependent than those used by other investigators. Next, the absolute magnitudes of the delayed neutron emission rates are calculated for the first time without takirig into account the angular momentum. The general trends of the observed emission rates for many nuclides can be well explained. Furthermore, the energy spectra of delayed neutrons are calculated for several examples in consideration of the angular momentum. These results show that the gross theory of {.1-decay is favorably applicable to the study of delayed neutrons.

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“…In the case of commutator method, it seems difficult to include both the forward and backward correlations on the same footing, although not impossible in principle 16 ) while the present procedure has no difficulty in taking into account both types of correlations. However, in compensation for the latter benefit a merit of the commutator method that the transition operator always appears as the comutator with H was discarded.…”

Section: -I Fujitamentioning

confidence: 97%

Approximation Method Based on Identities for Calculating Nuclear Matrix Elements. I

Fujita

1972

Prog. Theor. Phys.

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523The approximation method using projection operators, which was previously proposed and applied to calculations of hindered beta matrix elements, is reexamined from a more general viewpoint and extended to a method suitable to include both backward and forward correlations. The present method is compared with the previous methods, especially the RPA in the pairing model. New formulae are applicable not only to the hindered matrix elements but also to unhindered matrix elements. . The merit of the present method is that the coherent effect of small admixtures in wave functions is expressed as sum rules, which can also be regarded as semi-phenomenological parameters, and the way to estimate neglected terms is clearly seen because the method is based on identities. §I. IntroductionIt is well known 1 > that small admixtures in nuclear wave functions frequently change the magnitude of nuclear matrix elements drastically. A coherent effect of small admixtures is sometimes referred to as the core polarization effect.Previously an approximation method treating the commutator [H, m] instead of the original transition operator m was proposed 2 ) and the physical meaning of the method was discussed from various viewpoints.s), 4 )' >The method is useful if the important part of the nuclear Hamiltonian H commutes with the operator m, and using it the hindered beta matrix elements have been analysed. 2 >' 4 )~s) For the Gamow-Teller (GT) matrix elements f rr many examples were found for which experimental ft-values can be successfully explained.However, this method treats the initial and final wave functions asymmetrically, so that it is not very convenient for treating the forward and backward correlations on the same footing. On the other hand, the so called Random Phase Approximation 9 ),lo) (RPA) is suitable for including the backward correlations for simplified model interactions. In the case of the first or higher forbidden beta transitions, it is clear 11 )' 12 ) that the backward correlations play an important role.The purpose of this paper is to reexamine the commutator method from a more general viewpoint: Possible theoretical errors for calculating nuclear matrix elements are kept properly in mind. The present method is applicable to the diagonal as well as non-diagonal, unhindered as well as hindered matrix elements, at University of Ulster at Coleraine on April 14, 2015 http://ptp.oxfordjournals.org/ Downloaded from

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Nuclear Structure Studied from Weak and Related Processes

Cited by 24 publications

References 145 publications

The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

Application of the Gross Theory of β-Decay to Delayed Neutron Emissions

Approximation Method Based on Identities for Calculating Nuclear Matrix Elements. I

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