Neutrino Oscillation Search  Neutrino Experiments at Reactors  Reactors as Neutrino source

Status of deuteron experiments

The main goal of these experiments is the measurement of the cross section of the Neutral Current on Deuteron (single neutron in the final state): $\bar \nu_{e} + d \longrightarrow \bar \nu_{e} + p + n$ In addition the Charged Current reaction on the Deuteron (two neutrons in the final state) can be measured: $\bar \nu_{e} + d \longrightarrow e^{+} + n + n$ The knowledge of these cross sections is a unique probe of the axial-vector contribution to the neutral current. The accuracy of these experiments has been limited to $15\%$ due to the single neutron background induced by cosmic ray muons. In the UCI experiment installed at the Bugey site the single neutron background is low (60 neutrons per day) while the expected $\nu$ rate is 35 per day. An accuracy of $5\%$ (equivalent to the theoretical expectation) will be obtained in 1997. It can be seen that the neutron background induced by cosmic rays can be eliminated by an appropriate shielding. This is encouraging for future low background experiments near reactors. Another experiment is running at Krasnoyarsk at a larger distance (34 m.) The background is large (220 neutrons per day) and the expected rate lower (15 per day). They will obtain an accuracy of $10\%$ within few years.