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Pi-mesonic and Nonmesonic Weak Decays of Double-Lambda Hypernuclei

双 Lambda 超核的 Pi 介子和非介子弱衰变

基本信息

批准号：
13640294
负责人：
ITONAGA Kazunori
金额：
$ 0.45万
依托单位：
Miyazaki Medical College
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640294/
关键词：
hypernuclei weak decay decay rate pion spectra

项目摘要

The decay mechanism, decay rates and excitation spectra of π-mesonic and nonmesonic weak decays of double-Λ hypernuclei have been studied.1. Two decay modes exist in the nonmesonic weak decays of the double-Λ hypernuclei, I. e., the nucleon-induced weak decay and the hyperon-induced one. We have shown that the correlated-2π exchange (2π/σ and 2π/ρ) interactions in addition to the 1π are important in understanding the nucleon-induced ΛN→NN decays. Further we incorporate the ω and K exchanges in our model. Our decay interaction model can explain the decay rates and the decay rate ratios Γ_n/Γ_p of single-Λ hypernuclei well.2. The meson-exchange interaction model is applied to evaluate the nucleon-induced decay rate of ^6_<ΛΛ>He. Calculated decay rate is found to be smaller than twice that of ^5_Λhe, which may be related to the ΛΛ-cluster structure effect in ^6_<ΛΛ>He.3. The hyperon-induced ΛΛ→Nλ and ΛΛ→P?^-, N?^Ο are new modes seen in the double-Λ hypernuclei. We have derived the decay interaction potentials based on the meson exchanges. The 2π/σ, 1ω and 1K exchanges contribute to theΛΛ→Nλ potential, while the 1π, 2π/ρ and 1K exchanges do to theΛΛ→NΣ one. By adopting these potentials the decay rates of ^6_<ΛΛ>He and ^<10>_<ΛΛ>Be are evaluated to be 5% and 3% of the free Λ decay rate, respectively. The hyperon-induced decay rates of the double-Λ hypernuclei would be detectable in the future experiments.4. The pion spectra and the π-decay rates of ^6_<ΛΛ>He and ^<10>_<ΛΛ>Be are re-discussed. The π^- and π^Ο excitation specta of ^<10>_<ΛΛ>Be are newly calculated. The low-lying 1^- states reached via the spin-nonflip transitions from the parent hypernuclear ground state are strongly excited and form the sharp peaks. Such characteristics may be utilized to identify the double-Λ hypernuclear formation and/or to determine the spins of danghter hypernuclei.

研究了双Λ超核的π-介子和非介子弱衰变的衰变机制、衰变率和激发谱。在双Λ超核的非介子弱衰变中存在两种衰变模式：Ⅰ.例如，核子诱导弱衰变和超子诱导弱衰变。我们已经指出，除了1π相互作用外，关联的2π交换（2π/σ和2π/ρ）相互作用对理解核子引起的ΛN→NN衰变也是重要的.此外，我们在我们的模型中加入了ω和K交换。我们的衰变相互作用模型可以很好地解释单Λ超核的衰变率和衰变率比Γ_n/Γ_p.用介子交换相互作用模型计算了^6_<ΛΛ>He的核子感生衰变率。计算的衰变率小于^5_Λhe的两倍，这可能与^6_<ΛΛ> He的ΛΛ-团簇结构效应有关.超子诱导的ΛΛ→Nλ和ΛΛ→P？^-，N？O是在双Λ超核中发现的新模。我们导出了基于介子交换的衰变相互作用势。2π/σ、1ω和1 K交换对ΛΛ→Nλ势有贡献，而1π、2π/ρ和1 K交换对ΛΛ→N λ势有贡献。采用这些势，计算出^6_<ΛΛ>He和^<10>_<ΛΛ>Be的衰变率分别为自由Λ衰变率的5%和3%。在未来的实验中，双Λ超核的超子衰变率将是可探测的.本文重新讨论了^6_<ΛΛ>He和^ _<ΛΛ>Be的π能谱和π衰变率<10>。本文重新计算了^ _<ΛΛ>Be的π^-和π^O激发谱<10>。从母体超核基态通过自旋非翻转跃迁到达的低位1^-态被强烈激发并形成尖锐的峰。这样的特征可以用于识别双Λ超核形成和/或确定更危险的超核的自旋。