Hypernuclear Weak Decays
Hypernuclear Weak Decays
复制标题
DOI：
10.1143/ptps.185.252
复制
发表时间：
2010-06
影响因子：
--
通讯作者：
K. Itonaga;T. Motoba
中科院分区：
文献类型：
--
作者：
K. Itonaga;T. Motoba
近年来，对Λ-超核弱衰变（包括非介子和π-介子衰变）的理论研究取得了进展，其目的是揭示实验衰变观测值与基本弱衰变相互作用和弱衰变机制之间的联系。在壳模型框架下给出了极化超核质子的非介子衰变率Γnm和衰变不对称性参数α1的表达式。然后介绍了介子理论上的ΛN → NN相互作用，包括单介子交换、关联2π交换和手征对介子交换。讨论了介子交换势的性质及其在非介子衰变中的作用。采用π + 2π/ρ + 2π/σ + ω + K + ρπ/a1 + σπ/a1交换势，对轻重超核的非介子衰变观测值进行了系统的计算.该模型能很好地解释发射质子的衰变率、Γn/Γp比和内禀不对称性参数αΛ（αΛ与α1相关）的实验数据，且在误差范围内是一致的。通过将总弱衰变率Γtot = Γπ+Γnm转换为τ，计算了超核寿命，结果表明，当超核质量A ≥ 30时，超核寿命具有饱和性质，除极轻超核外，超核寿命与实验值基本一致.最后指出了模型的进一步扩展和存在的问题。本文简要介绍了π介子弱过程，并将计算结果与预测结果进行了比较，并用最近的高精度FINUDA π介子衰变数据进行了验证。这表明，理论基础似乎是牢固的。
The recent theoretical studies of Λ-hypernuclear weak decays of the nonmesonic and π-mesonic ones are developed with the aim to disclose the link between the experimental decay observables and the underlying basic weak decay interactions and the weak decay mechanisms. The expressions of the nonmesonic decay rates Γnm and the decay asymmetry parameter α1 of protons from the polarized hypernuclei are presented in the shell model framework. We then introduce the meson theoretical ΛN → NN interactions which include the one-meson exchanges, the correlated-2π exchanges, and the chiral-pair-meson exchanges. The features of meson exchange potentials and their roles on the nonmesonic decays are discussed. With the adoption of the π + 2π/ρ + 2π/σ + ω + K + ρπ/a1 + σπ/a1 exchange potentials, we have carried out the systematic calculations of the nonmesonic decay observables for light-to-heavy hypernuclei. The present model can account for the available experimental data of the decay rates, Γn/Γp ratios, and the intrinsic asymmetry parameters αΛ (αΛ is related to α1) of emitted protons well and consistently within the error bars. The hypernuclear lifetimes are evaluated by converting the total weak decay rates Γtot = Γπ+Γnm to τ , which exhibit saturation property for the hypernuclear mass A ≥ 30 and agree grossly well with experimental data for the mass range from light to heavy hypernuclei except for the very light ones. Future extensions of the model and the remaining problems are also mentioned. The π-mesonic weak processes are briefly surveyed, and the calculations and predictions are compared and confirmed by the recent high precision FINUDA π-mesonic decay data. This shows that the theoretical basis seems to be firmly grounded.