标题： 中性双超核$_{ΛΛ}^{4}$n 是否已被观测到？ 显示英文标题

标题： Has the neutral double hypernucleus $_{ΛΛ}^{4}$n been observed?

摘要： 布鲁克海文国家实验室-加速器质子源E906实验是第一个完全电子化的实验，它产生了大量统计数据并研究了双超核。 在相关$\pi^-$--$\pi^-$动量矩阵中观察到了两个主要结构，在 (p$_{\pi-H}$,p$_{\pi-L}$) = (133,114) MeV/c 和 (114,104) MeV/c 处。 在本工作中，我们认为将 (133,114) MeV/c 处的结构解释为$^3_{\Lambda}$H+$^4_{\Lambda}$H 对是值得怀疑的。 我们证明，无论是超核在停止的$\Xi^-$被$^9$Be 核捕获之后产生，还是高能$\Xi^-$与靶材中的$^9$Be 核发生相互作用，都不能产生足够多的这类双子对。 因此，我们探讨了阿布拉罕·加尔提出的假设，即$_{\Lambda\Lambda}^{4}$n 的衰变可能负责观察到的结构。 确实，在统计多重碎片化模型中包含具有 50% 两体$\pi^-$分支比的$_{\Lambda\Lambda}^{4}$n，可以很好地描述 E906 数据。 另一方面，一个边界$^{3}_{\Lambda}$核会使得动量关联矩阵中出现显著的结构，这与 E906 的观测结果明显不一致。 显示英文摘要

摘要： The BNL-AGS E906 experiment was the first fully electronic experiment to produce and study double hypernuclei with large statistics. Two dominant structures were observed in the correlated $\pi^-$--$\pi^-$ momentum matrix at (p$_{\pi-H}$,p$_{\pi-L}$) = (133,114) MeV/c and at (114,104) MeV/c. In this work we argue that the interpretation of the structure at (133,114) MeV/c in terms of $^3_{\Lambda}$H+$^4_{\Lambda}$H pairs is questionable. We show, that neither a scenario where the hypernuclei are produced after capture of a stopped $\Xi^-$ by a $^9$Be nucleus nor interactions of energetic $\Xi^-$ with $^9$Be nuclei in the target material can produce a sufficient amount of such twin pairs. We have therefore explored the conjecture of Avraham Gal that decays of the $_{\Lambda\Lambda}^{4}$n may be responsible for the observed structure. Indeed, the inclusion of $_{\Lambda\Lambda}^{4}$n with a two-body $\pi^-$ branching ratio of 50 % in a statistical multifragmentation model allows to describe the E906 data remarkably well. On the other hand, a bound $^{3}_{\Lambda}$n nucleus would cause a striking structure in the momentum correlation matrix which is clearly inconsistent with the observation of E906.