Geneva

A major project to send a beam of muon neutrinos from Geneva under the Alps to the Gran Sasso laboratories near Rome was approved last week by the council of CERN, the Geneva-based European Laboratory for Particle Physics.

Italy's INFN, its national organization for particle physics, is organizing two experiments, known as OPERA and ICANOE, to study the oscillations of the neutrinos during their 730-km trip to Gran Sasso.

The experiments are designed to extend the breakthrough results achieved at the SuperKamiokande (Super-K) experiment in Japan last year, which showed that a proportion of muon neutrinos from cosmic rays disappeared, presumed to have been converted to tau neutrinos, as the beam travelled through the Earth (see Nature 394, 13; 1998). The Gran Sasso experiments will be optimized to detect tau neutrinos directly.

The neutrino beamline will cost SFr71 million (US$45 million), of which INFN will pay around two-thirds. Special donations from other CERN member states, including Germany, Switzerland and France, will provide SFr16 million. First experimental results will be collected in 2005.

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Direct route: the beam could solve some puzzles about neutrinos on its 2.5-millisecond journey.

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The idea has been under discussion for many years; Italian particle physicists have long been disappointed at being left behind. Japan and the United States are planning neutrino experiments using long-range accelerated beams in an attempt to repeat the Super-K results under more controlled conditions. But these will only look for disappearance of muon neutrinos, says Lorenzo Foa, professor of particle physics at the Scuola Normale Superiore, in Pisa, and a former director of research at CERN. “We will still need the positive confirmation of measuring the creation of tau neutrinos,” he says, adding that Japan itself has expressed interest in participating in the experiments.

The approval also gives a shot in the arm to the INFN's laboratories in Gran Sasso. Built in the 1970s, they were deliberately orientated towards CERN in the hope that a neutrino beam would one day be created.

Luciano Maiani, the director-general of CERN, says that the quality of the planned neutrino beam and the innovative experiments being designed offer unique opportunities for science.