Evaluation of effect coefficient for each factor affecting time variations in underground muon count rate

Underground cosmic-ray muon count rates always change with time due to variations in various kinds of meteorological factors and solar activity. The main factors are atmospheric pressure, force field potential and temperature in the upper atmosphere. The pressure and force field potential effect coefficients are evaluated as a function of depth under the ground through theoretical calculations based on a continuous slowing down approximation for energy-angle double differential spectra. The temperature effect coefficient is derived from ground-observed data analyses in relation to the temperature in the upper atmosphere. (author)