Comprehensive study of dark matter beyond WIMP paradigm

在JSPS研究计划的第二年，我主要对轴子样粒子（ALP）的其他应用感兴趣。今年9月，我应国立台湾师范大学陈传仁教授的邀请进行了一次学术访问。在此期间，陈教授想用ALP来解释MiniBooNE类电子事件的过量。MiniBooNE是位于费米实验室的一项实验。最近，他们用更多的数据和新的背景分析更新了他们的结果。在这个项目中，我们假设ALP只与一个电子和一个无菌中微子耦合。在适当的参数区域内，我们的模型可以拟合MiniBooNE的超量。我们的策略如下。首先，来自费米实验室助推器的质子束撞击铍靶，在那里产生大量介子，如介子和介子。通过活性中微子和惰性中微子的混合，介子可以衰变成带电的轻子和惰性中微子，惰性中微子会行进几百米到达MiniBooNE探测器。在探测器区域内，惰性中微子将通过中微子混合衰变为活性中微子和ALP， ALP随后将衰变为电子-正电子对，可以模拟类电子事件。原因是MiniBooNE传感器无法区分准直的电子-正电子对和单个电子。为了使我们的想法有效，我们还必须检查我们发现的参数空间是否与观测结果一致，例如碰撞转储实验和超新星爆炸。

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.