Comprehensive study of dark matter beyond WIMP paradigm

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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.