Reactor-based neutrino oscillation experiments

The status of neutrino oscillation searches employing nuclear reactors as sources is reviewed. This technique, a direct continuation of the experiment that proved the existence of neutrinos, is today an essential tool in investigating the indications of oscillations found in studying neutrinos produced in the sun and in the earth's atmosphere. The low energy of the reactor (nu) over bar (e), makes them ideal for exploring oscillations with small mass differences and relatively large mixing angles. In the last several years the determination of the reactor antineutrino flux and spectrum has reached a high degree of accuracy. Hence measurements of these quantities at a given distance L can be readily compared with the expectation at L = 0, thus testing the disappearance of (nu) over bar (e). Two recent experiments, CHOOZ and PALO VERDE, with baselines of about 1 km and sensitive to the neutrino mass differences associated with the atmospheric neutrino anomaly have collected data and published results recently. An ambitious project with a baseline of more than 100 km, KAMLAND, has now began to take data. This last reactor experiment will have a sensitivity sufficient to explore part of the oscillation phase space relevant to solar neutrino scenarios. It is the only envisioned experiment with a terrestrial source of neutrinos capable of addressing the solar neutrino puzzle.