Neutrino Experiments at Reactors  Neutrino physics at accelerators  The COSMOS experiment at

Long base-line experiments at accelerators

If the atmospheric neutrino problem is the result of $\nu_{\mu} - \nu_{\tau}$ oscillations, then the value of $\Delta$m $^{2} \approx 10^{-2}$eV² needed to explain the data will give rise to oscillations which can be detected by installing a suitable detector at a distance of the order of 1000 km from a source of neutrinos with energies of the order of 10 GeV. The first long baseline accelerator experiment to address this problem will use a wide-band neutrino beam from the KEK 12 GeV proton synchrotron in conjunction with the Super-Kamiokande detector at a distance of 250 km. Both $\nu_\mu$ disappearance and $\nu_e$ appearance will be studied. This experiment should start data taking at the beginning of 1999. The future neutrino programme at Fermilab includes a long base-line experiment. The neutrino beam from the Main Injector is directed towards the Soudan underground laboratory in Minnesota at a distance of 730 km from Fermilab. The Soudan laboratory will be equipped with a new underground hall oriented along the neutrino beam where the Main Injector Neutrino Oscillation Search (MINOS) will be installed. The MINOS detector consists of magnetised iron plates interleaved with active detector planes providing at the same time calorimetric and tracking information. The total mass of the MINOS detector is 10,000 tons. With such a mass and a wide-band beam, one expects approximately 20,000 $\nu_\mu$ CC events per year. The MINOS detector is used in conjunction with a second detector of similar conceptual design but with a much smaller mass located at a distance of $\sim$ 1 km from the proton target. MINOS will begin data taking at the beginning of the next century in parallel with the short base-line COSMOS experiment described previously. It will be able to demonstrate the presence of $\nu_\mu$ oscillations for mixing angles $\sin^{2}2\theta > 0.01$ and for $\Delta$m ² > 10^-3 eV ². Another possibility for long base-line neutrino oscillation searches, which has been recently proposed consists in aiming a neutrino beam from the CERN SPS to Gran Sasso National Laboratory in Italy at a distance of 732 km. The three existing underground halls at Gran Sasso, under $\sim$ 4000 m of water equivalent, are already oriented towards CERN and ICARUS, a 600 tons detector suitable for oscillation searches, will start operation in 1999 with the main goals of searching for proton decay and of studying atmospheric and solar neutrinos. ICARUS is a new detector concept based on a liquid Argon Time Projection Chamber (TPC) which allows three-dimensional reconstruction of events with spatial resolution of the order of 1 mm.