Sage: The Soviet-American gallium solar neutrino experiment
A radiochemical 71Ga-71Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Academy of Sciences of the USSR. The number of 71Ga atoms extracted from thirty tons of gallium was measured in five runs during the period of from January to July 1990 and in June run og 1991. Assuming that the extraction efficiency for 71Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed for measurements of 1990 the product of the neutrino flux and the cross section for all sources of neutrinos to be 20+15/-20(stat.)± 32(syst) SNU, resulting in a limit of less than 79 SNU (90% CL). The analysis of the combined data sets of 1990 and preliminary data of June run of 1991 results in a limit of less than 63 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model. © 1992.