Comprehensive study of dark matter beyond WIMP paradigm

在JSPS研究计划的第二年，我主要对轴子类粒子(ALP)的其他应用感兴趣。今年九月，我应国立台湾师范大学陈传仁教授的邀请，进行学术访问。在此期间，陈教授希望用ALP来解释类电子事件的MiniBooNE过剩现象。MiniBooNE是一项位于费米实验室的实验。最近，他们更新了结果，增加了数据和新的背景分析。在这个项目中，我们假设ALP只与一个电子和一个稀有的中微子耦合。在适当的参数范围内，我们的模型可以很好地拟合MiniBooNE过剩。我们的战略如下。首先，来自费米实验室助推器的质子束击中了铍目标，在那里产生了大量的介子，如Kaon和pion。通过活跃的中微子和稀有中微子的混合，介子可以衰变成带电的轻子和稀有的中微子，而不带电的中微子将旅行几百米到达MiniBooNE探测器。在探测器区域内，稀薄的中微子将通过中微子的混合衰变为活跃的中微子和ALP，而ALP随后将衰变为能够模拟类电子事件的电子-正电子对。原因是，MiniBooNE传感器无法区分准直电子-正电子对和单电子。为了使我们的想法有效，我们还必须检查参数空间，我们发现的参数空间与观察到的结果是一致的，例如撞击-倾倒实验和超新星爆炸。

In the second year of the JSPS research program, I am mainly interested in other applications of the axion-like particles (ALP). This September, I was invited by Prof. Chuan-Ren Chen at National Taiwan Normal University (NTNU) to have an academic visit. During this period, Prof. Chen wants to explain the MiniBooNE excess of electron-like events by using the ALP. The MiniBooNE is an experiment located at Fermilab. Recently, they have updated their results with increased data and new background analyses. In this project, we assume that the ALP only couples to an electron and a sterile neutrino. In a proper parameter region, our model can fit the MiniBooNE excess. Our strategy is as follows. First, the proton beam from the Fermilab booster hitting on a beryllium target, where a lot of mesons such as kaon and pion are produced. Through the mixing between the active neutrinos and sterile neutrino, the meson can decay into a charged lepton and a sterile neutrino, and the sterile neutrino would travel a few hundred meters and arrive at the MiniBooNE detector. Inside the detector region, the sterile neutrino would decay into an active neutrino and an ALP via the neutrino mixing, and the ALP would subsequently decay into an electron-positron pair that can mimic the electron-like events. The reason is that the MiniBooNE sensors cannot distinguish a collimated electron-positron pair from a single electron. For our idea to be valid, we also have to examine the parameter space we find is consistent with the observations such as bump-dump experiments and supernova explosions.