Supernova relic neutrino detection with neutron tagging

当一颗大质量恒星耗尽所有燃料来源时，它的存在将以核心塌缩的超新星爆炸而告终。这一事件涉及到所有四种自然力量，到目前为止还没有被很好地理解。在核心崩塌期间，恒星99%以上的引力能量被转化为中微子。到目前为止，我们只探测到一次来自SN1987A的超新星中微子爆发。由于中微子实际上永远在旅行，宇宙中应该充满了来自所有爆发过的核心坍塌超新星的中微子的各向同性信号。这些中微子被称为超新星遗迹中微子(SRN)，尚未被观测到。主要的SRN相互作用是逆β衰变，其中一个电子反中微子与一个自由质子相互作用，产生一个正电子和一个中子。最近将Gd装载到Super-Kamiokande水切伦科夫探测器中，除了正电子信号外，还可以检测到中子。这种符合标记是一种强大的工具，可以去除阻碍SRN检测的先前不可还原的背景。在他的博士学位期间，这名学生将作为Super-Kamiokande协作的成员进行第一次SRN检测。这是朝着收集高统计样本迈出的第一步，然后可以用来确定宇宙的超新星历史。

When a massive star exhausts all sources of fuel, its existence ends in a core-collapse supernova explosion. This events involve all four forces of nature and, as yet, are not well understood. During the core-collapse, over 99% of the gravitational energy of the star is converted into neutrinos. To date, we have only detected one burst of supernova neutrinos, from SN1987a. Since the neutrinos effectively travel forever, the universe should be filled with an isotropic signal of neutrinos from all of the core-collapse supernovae that have ever exploded. These neutrinos are known as "supernova relic neutrinos" (SRN) and have not yet been observed. The primary SRN interaction is inverse beta decay, in which an electron antineutrino interacts with a free proton to produce a positron and a neutron. The recent loading of gadolinium into the Super-Kamiokande water Cherenkov detector allows the neutron to be detected, in addition to the positron signal. This coincidence tagging is a powerful tool for removing the previously irreducible backgrounds that have prevented SRN detection. During his PhD, the student will work as a member of the Super-Kamiokande collaboration to make a first detection of the SRN. This is the first step towards collecting a high-statistics sample, which can then be used to determine the supernova history of the universe.