arXiv 2011.049922020-11nucl-thnucl-ex

$^{19}$ B的三体结构：双中子晕核的射程效应

Three-body structure of $^{19}$B: Finite-range effects in two-neutron halo nuclei

J. Casal, E. Garrido

备注：: 6 pages, 3 figures, 1 table. Rapid Communication. Updated version
发表信息：: Phys. Rev. C 102, 051304 (2020)
DOI：: 10.1103/PhysRevC.102.051304

摘要：

在$^{17}\text{B}+n+n$模型中研究了$^{19}$ B的结构和$B(E1)$跃迁强度，最近的实验表明$^{19}$ B具有明显的双中子晕结构。通过采用接触$n$ - $n$相互作用对实验数据进行了初步分析，已知接触$n$ - $n$相互作用低估了其他晕核（如$^{11}$ Li）中的$s$波含量。本文采用有限程两体相互作用的三体超球理论来描述$^{19}$ B。特别地，将使用两种不同的有限范围$n$ - $n$相互作用，以及范围逐渐减小的简单中心高斯势。目的是确定细胞核的主要性质，并研究它们在使用接触式$n$ - $n$电位时如何变化。还特别注意依赖于用于解释三体效应的处方，即，三体力或密度依赖性$n$ - $n$势。我们发现，三体模型加上有限程势提供了一个与实验数据一致的描述$^{19}$ B。结果基本上是独立的两体电位的短距离的细节，从而产生约55%的$(s_{1/2})^2$含量，明显大于最初的估计。人们也发现，对用于三体效应的处方的依赖性很小。总的计算$B(E1)$强度与实验结果是兼容的，虽然我们稍微高估了周围的低能量峰值的$dB(E1)/d\varepsilon$分布的数据。最后，我们表明，减少的$n$ - $n$的相互作用范围产生了显着减少的$s$ -波的贡献，然后应该预期在计算中使用接触相互作用。

英文摘要：

The structure and $B(E1)$ transition strength of $^{19}$B are investigated in a $^{17}\text{B}+n+n$ model, triggered by a recent experiment showing that $^{19}$B exhibits a well pronounced two-neutron halo structure. Preliminary analysis of the experimental data was performed by employing contact $n$-$n$ interactions, which are known to underestimate the $s$-wave content in other halo nuclei such as $^{11}$Li. In the present work, the three-body hyperspherical formalism with finite-range two-body interactions is used to describe $^{19}$B. In particular, two different finite-range $n$-$n$ interactions will be used, as well as a simple central Gaussian potential whose range is progressively reduced. The purpose is to determine the main properties of the nucleus and investigate how they change when using contact-like $n$-$n$ potentials. Special attention is also paid to the dependence on the prescription used to account for three-body effects, i.e., a three-body force or a density-dependent $n$-$n$ potential. We have found that the three-body model plus finite-range potentials provide a description of $^{19}$B consistent with the experimental data. The results are essentially independent of the short-distance details of the two-body potentials, giving rise to an $(s_{1/2})^2$ content of about 55%, clearly larger than the initial estimates. Very little dependence has been found as well on the prescription used for the three-body effects. The total computed $B(E1)$ strength is compatible with the experimental result, although we slightly overestimate the data around the low-energy peak of the $dB(E1)/d\varepsilon$ distribution. Finally, we show that a reduction of the $n$-$n$ interaction range produces a significant reduction of the $s$-wave contribution, which then should be expected in calculations using contact interactions.

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