Gamow-Teller Transitions Ruling the Supernova Explosion

伽莫夫泰勒跃迁决定超新星爆炸

基本信息

批准号：
15540274
负责人：
FUJITA Yoshitaka
金额：
$ 2.24万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

In the core-collapse stage of type II supernovae, weak-interaction processes of pf-shell nuclei play important roles. Therefore, studies of electron capture and beta decay caused by charged currents and neutrino-nucleus scattering caused by neutral currents are of great astrophysical interest. The charged-current processes are dominated by Fermi and Gamow-Teller (GT) transitions, but the knowledge for the important GT transitions in pf-shell nuclei is very poor. Direct information on the GT transition strength B(GT) can be derived from beta-decay measurements. However, B(GT) values were derived for at most a few low-lying states with large ambiguities.Charge-exchange (CE) reactions can access to GT transitions at higher excitations. In particular, it was shown that measurements at scattering angles around 0 deg and at intermediate beam energies above 100 MeV/nucleon were good probes of GT transitions. A development in precise beam matching techniques realized an energy resolution of about 30 keV in intermediate energy (311e, t) reactions at 0 deg. With this one-order of magnitude better resolution, we can now study GT and Fermi states that were unresolved in the pioneering (p, n) reactions. We performed experiments on T=1 targets 46Ti, 50Cr, 54Fe, and Ni isotopes 58Ni, 6ONi, 62Ni, and 64 Ni, and some additional reference nuclei. The B(GT) values have been extracted for some of the nuclei. The obtained strength distributions were compared with results of theoretical calculations. It was found that the modern shell-model calculations can reproduce the gross features of the distribution, but not the details.We plan to extend studies for a wider range of pf-shell nuclei, and the results will put restrictions on the theoretical studies of supernova explosion and also for the element synthesis.

在II型超新星的核心崩溃阶段，PF壳核的弱交互过程起着重要作用。因此，由中性电流引起的电流电流和中微子核散射引起的电子捕获和β衰变的研究极具天体物理感兴趣。带电的流动过程由费米和游戏性 - 泰勒（GT）过渡主导，但是PF-shell Nuclei中重要的GT转变的知识非常差。有关GT过渡强度B（GT）的直接信息可以从β-末期测量中得出。但是，在最多几个具有较大歧义的低洼状态下得出了b（gt）的值。电动交换（CE）反应可以在更高的激发下访问GT转变。特别是，表明在0度左右的散射角度和高于100 meV/核的中间光束能量的测量值是GT转变的良好探针。精确的光束匹配技术的开发实现了在0度处的中间能量（311e，t）反应中约30 keV的能量分辨率。通过这个一阶更好的分辨率，我们现在可以研究在开拓性（P，N）反应中未解决的GT和Fermi状态。我们在T = 1目标46TI，50CR，54FE和Ni同位素58NI，6ONI，62NI和64 Ni上进行了实验，以及一些其他参考核。已经为某些核提取了B（GT）值。将获得的强度分布与理论计算结果进行了比较。发现现代的壳型计算可以重现分布的总特征，但不是细节。我们计划扩展对PF壳核的研究，结果将对超新星爆炸的理论研究以及元素合成的理论研究施加限制。