Hyperon Superfluidity in Neutron Star Cores

如果实现中子星星核超子的超流性，“超子冷却”可能成为某些低表面温度中子星快速冷却方案的一个有希望的候选方案。这个研究项目的目的是研究超子超流体是否可能。到目前为止（2001 ~ 2002），我们（1）阐明了超子混合的发生机制，提出了一个具有超子混合核的中子星星模型;（2）在（1）和（2）的基础上，确定了重子各分量（n，p，Λ，π ^-）的超流密度区。2003年取得的最新成果如下：1.我们得到了各种ν-发射过程（修正的URCA，库珀对，核子直接URCA，超子直接URCA）的ν-发射率，并根据密度ρ阐明了什么是最有效的。从而为中子星星冷却的计算提供了基本的物理输入，并指出在^3P_2 n超流性中核子直接URCA过程是被禁止的，而铜对过程占主导地位。我们已经证明，如果最近由^6_<ΛΛ>He提出的“较低吸引力的ΛΛ相互作用”，即所谓的“NAGARA事件”成立，那么Λ-超流性消失，“超子冷却”说就不成立了。如果可能的话，由于Λ Λ ^-配对（而不是ΛΛ一）而导致的Λ-超流体的复兴是克服这个问题的一种方法，也是我们即将到来的主题。

The "hyperon cooling" can be a promising candidate for a rapid cooling scenario demanded for some neutron stars with low surface temperature, if superfluidity of hyperons admixed in neutron star cores is realized. The aim of this research project is to study whether hyperon superfluids can be possible or not. So far (2001〜2002), (1) we clarified the mechanism for the occurence of hyperon mixing and proposed a realistic neutron star model with a hyperon-mixed core, and (2) determined the superfluid density-regions for respective baryon components (n, p, Λ, Σ^-), on the basis of the results for (1) and (2). The results newly obtained in 2003 are as follows.1. We have obtained ν-emissibities for various ν-emission processes (modified URCA, Cooper-pair, nucleon direct-URCA, hyperon direct-URCA) and clarified what is most effective according to the density ρ. Thus we have provided the basic physical inputs for neutron star cooling calculations and pointed out that the nucleon direct-URCA process is forbidden and the cooper-pair process dominates in the ^3P_2 n-superfluidity.2. We have shown that the Λ-superfluidity disappears and hence the "hyperon cooling" scenario breaks down, if "less attractive ΛΛ interaction" suggested very recently by ^6_<ΛΛ>He, a so-called "NAGARA event" is true. A revival of Λ-superfluid due to ΛΣ^-pairing (instead of ΛΛ one), if possible, is a way to overcome the problem and is our forthcoming subject.