Research on the energy resolution of neutrinoless double beta decay experiment DCBA

双贝塔衰变是原子中的原子核发射两条贝塔射线，并将其原子序数增加两个单位的现象。在这种情况下，2vββ意味着发射两个反电子中微子和两条β射线，而0vββ代表没有中微子发射，因此被称为无中微子双β衰变。到目前为止，已经观测到了几个原子的2vββ‘S，并测量了它们的半衰期，但还没有观测到Ovββ。如果中微子是马约拉纳粒子，则应该发生Ovββ。也就是说，观测到Ovββ意味着中微子是马约拉纳粒子，测量其寿命可以确定中微子的绝对质量尺度。这有助于建立超越旧标准模型的新的基本粒子理论，同时，对Ovf3f3的观测将支持瘦子发生理论，该理论被认为是早期宇宙情景的有力候选者。漂移室Beta-ray Analyzer(漂移室Beta-ray Analyzer)实验通过漂移室跟踪探测器测量均匀磁场中每条β射线的动量。这是迄今为止在其他地方没有实现的唯一方法。DCBA暗室只对带电粒子敏感，因此可以从本质上消除伽马射线本底。由于磁场的存在，使得电子、正电子和α粒子之间的粒子识别变得非常容易，并且对于剔除带电粒子背景非常有效。在本研究中，使用名为DCBA-T2的原型证实了这一点。DCBA-T2揭示了提高能量分辨率的方法，这是分离Ovββ事件和2vββ事件的关键问题。然后，在DCBA-T2经验的基础上，新的原型DCBA-T3正在建造中。为了寻找具有大量衰变源的Ovββ事件，计划在未来计划一个扩大的探测器模块。

Double beta decay is the phenomenon that the nucleus in an atom emits two beta rays and increases its atomic number by two units. In this case, 2vββ means the emission of two anti-electron-neutrinos together with two beta rays, and 0vββ stands for no neutrino emission therefore it is called the neutrinoless double beta decay. So far 2vββ's of several atoms have been observed and their halflives have been measured, while no observation of Ovββ has been confirmed yet. If neutrinos are Majorana particles, Ovββ should take place. In other words, the observation of Ovββ means that neutrinos are Majorana particles, and the measurement of its haifiife can determine the absolute mass scale of neutrinos. This contributes to constructing the new theory of elementary particles beyond the old standard modeL And also, the observation of Ovf3f3 will support the leptogenesis theory, which is considered as the strong candidate of early universe scenario. The DCBA (Drift Chamber Beta-ray Analyzer) experiment measures the momentum of each beta ray in a uniform magnetic field by drift chamber tracking detectors. This is the unique method not realized elsewhere so far. The DCBA chamber is only sensitive to charged particles therefore it can intrinsically eliminate gamma ray backgrounds. Particle identification among electron, positron and alpha particle is easy because of the magnetic field, and it is very powerful for rejecting charged particle backgrounds. These have been confirmed using the prototype called DCBA-T2 in the present research. DCBA-T2 has revealed the method to improve the energy resolution, which is the key issue of separating Ovββ events from 2vββ events. Then new prototype DCBA-T3 is now under construction based on the experiences of DCBA-T2. In the future, an enlarged detector module is planed in order to search for Ovββ events with a large amount of decay sources.