Progress of muon science

Various scientific researches using muons have become active. In most cases, these sufficiently utilize the characteristics of positive and negative muons which behave as 'light protons' and 'heavy electrons'. The objects spread to the research on physical properties and materials by μSR process, the research on nuclear fusion using muon catalyst, the nondestructive elementary analysis by muon atomic X-ray, and basic physics studies. In this report, the recent interesting topics are outlined, and the research on low speed muon formation and the development of high intensity accelerators, which are expected to contribute largely to the advance of muon science, are described. Muons are the unstable elementary particles discovered first in cosmic ray, and the basic properties of muons are shown. The typical accelerators in the world which are used for muon scientific experiment are listed. The interaction of muons with solids, μSR and its application, the development of ultralow speed muons and their merits, the medical use of muon atom X-ray, the present state of the experiment and the theory of muon catalyzed fusion and the studies on muon science and accelerators are reported. (K.I.)