The BNO-LNGS joint measurement of the solar neutrino capture rate in 71Ga

We describe a cooperative measurement of the capture rate of solar neutrinos by the reaction 71Ga(νe, e−)71Ge. Extractions were made from a portion of the gallium target in the Russian-American Gallium Experiment SAGE and the extraction samples were transported to the Gran Sasso laboratory for synthesis and counting at the Gallium Neutrino Observatory (GNO). Six extractions of this type were made and the resultant solar neutrino capture rate was 64-22+24 SNU, which agrees well with the overall result of the gallium experiments. The major purpose of this experiment was to make it possible for SAGE to continue their regular schedule of monthly solar neutrino extractions without interruption while a separate experiment was underway to measure the response of 71Ga to neutrinos from an 37Ar source. As side benefits, this experiment proved the feasibility of long-distance sample transport in ultralow background radiochemical experiments and familiarized each group with the methods and techniques of the other.