2 HEMISPHERE OBSERVATIONS OF THE NORTH-SOUTH SIDEREAL ASYMMETRY AT APPROXIMATE-TO-1 TEV

A new underground muon telescope system installed at a depth of 154 m. w.e. at Liapootah, central Tasmania, has been continuously monitoring cosmic ray intensity since December 1991. In two hemisphere observatio ns, this telescope plays an important roll as a conjugate station to M atsushiro in Japan, which has been operating at a similar depth (220 m .w.e.) since April 1984. In this paper, we analyze data recorded at Li apootah during 33 months from January 1992 to October 1994, to test th e north-south asymmetry in the sidereal diurnal variation caused by ga lactic anisotropy of high energy cosmic ray intensity. We find average sidereal variation (0.041 +/- 0.006%, 3.5 +/- 0.6 hr) being observed by the vertical component telescope (median latitude of viewing lambda (E) = 36.2 degrees S). Comparison with the sidereal diurnal variation (0.028 +/- 0.006%, 2.6 +/- 0.8 hr) observed by Matsushiro (lambda(E) = 34.5 degrees N) during the same period confirms the existence of a no rth-south asymmetry in which the amplitude of the variation increases as the median direction of viewing moves southward over the equator. T his is the first positive result indicating the north-south sidereal a symmetry by two hemisphere observations.