COSMIC-RAY DEFICIT FROM THE DIRECTIONS OF THE MOON AND THE SUN DETECTED WITH THE TIBET AIR-SHOWER ARRAY

Data from the Tibet air-shower array were used to examine the cosmic-ray shadows of the Moon and the Sun at energies around 10 TeV. The shadowing effect was clearly observed at the 5.8sigma level for the Moon, while the shadow of the Sun was found in the direction away from the Sun by 0.86-degrees to the west and 0.43-degrees to the south. The effect of the geomagnetic field has also been observed in the shadow of cosmic rays by the Moon. The observed deflection of the Sun's shadow is briefly discussed in connection with the effect of the magnetic fields between the Sun and the Earth. This is the first observation of the effects of such magnetic fields on the cosmic-ray shadow. The maximum-likelihood analysis of the Moon data set shows that the angular resolutions of the array for showers with its mode energies 7 and 35 TeV are 0.87-degrees(-0.10-degrees-degrees)+0.13-degrees and 0.54-degrees(-0.08-degrees)+0.11-degrees, respectively.