NEUTRINO-RESONANT OSCILLATIONS IN THE EARTH, AND THE NU-E/NU-MU RATIO IN UPWARD-GOING ATMOSPHERIC NEUTRINO FLUXES

We evaluate the conversion probability for neutrinos by solving the evolution equations with a numerical method, taking into account a density distribution of the Earth, and calculate an upward-going neutrino flux ratio (v, + Fe)/(vy + YJ by using the recent values of atmospheric neutrino fluxes, where the updated ratios v 1; and vel;, have been taken into account. It is found that the ratio, including the effect of neutrino-resonant oscillations, can well Y explain the Kamiokande data for $ = 0" and 30°, and the NUSEX and the Frejus data (averaged over $1 at energies around 1 GeV, whilst the ratio with no neutrino oscillations or with the muon polarization cannot explain the measured data. © 1990 IOP Publishing Ltd.