INR RAS - international collaborations

• Particle physics - accelerator's experiments
• Particle physics - nonaccelerator's experiments
• Fundamental nuclear physics
• Research and design for charge particle accelerators
• Neutrino astrophysics, cosmic rays physics
• CERN

Neutrino astrophysics, cosmic rays physics -
Russia-USA Gallium-Germanium Experiment SAGE

  The experiment is carried out in the specially built underground laboratory at the Baksan Neutrino Observatory of INR RAS in Russia. The rock gives an overhead shielding equivalent to 4700 m.w.e. and reduces the muon flux by a factor of 10⁷. The SAGE data of 92 runs during a bit more than half the 22-year cycle of solar activity from January 1990 through December 2001 gives a capture rate of solar neutrinos in gallium metal with energy more than 233 keV

    70.8+5.3/-5.2(stat.)+3.7/-3.2(syst.)SNU

The predicted Standard Solar Model rate is 130 SNU.

The SAGE results combined with those of all other solar neutrino experiments have allowed us to make the first estimate of the electron neutrino pp flux that reaches the Earth of

    (4.6 ± 1.1)* 10¹⁰ n/(cm²*s)

Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is

    (7.7 ± 1.8)* 10¹⁰ n/(cm²*s)

in agreement with the standard solar model calculation:

    (5.95 ± 0.06)* 10¹⁰ n/(cm²*s)

To determine the oscillation parameters in the solar sector more precisely additional data are required, especially from the experiments which are sensitive to low energy neutrinos. SAGE continues to perform regular (every four weeks) solar neutrino measurements with 50 tons of gallium with reducing statistical and systematic uncertainties.