Time variation of the cosmic ray muon flux in underground detectors and correlation with atmospheric temperature

Time variations of the cosmic ray muon flux observed during the period from January 1987 to April 1990 in the Matsushiro underground muon observatory and the Kamiokande-II detector are compared. A significant correlation between the two observations is found. The observed variations are well explained as a temperature effect in the atmosphere based on precise atmospheric temperature measurements by the Wajima Observatory of the Japan Meteorological Agency. (author)