RESULTS FROM THE SOVIET-AMERICAN GALLIUM EXPERIMENT

A radiochemical Ga-71-Ge-71 experiment to determine the primary flux o f neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of Ge-71 atoms extracted from 30 tons of gallium in 1990 and 57 tons in 1991 was mea sured in twelve runs during the period of January 1990 to December 199 1. For the 1990 data, we observed the capture rate to be 20 + 15/-20 ( stat) +/- 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard So lar Model. The 1991 data, taken with 57 tons of gallium, shows a non z ero Ge-71 signal. A final result from the 1990 and 1991 data is still pending completion of studies of possible systematic effects.