Tracking neutrino oscillations

For Konrad Elsener and colleagues working at the Gran Sasso National Laboratory in central Italy, the idea of looking for a needle in a haystack must seem trivial by comparison. Their aim is to detect subatomic particles known as neutrinos that are fired in a beam from the CERN particle-physics laboratory in Geneva, travel 730 km through the Earth's crust in central Europe and arrive at their detector under the Gran Sasso mountain. Making such detections will be extremely difficult because neutrinos react so weakly with other matter – the researchers expect that of the roughly 1014 neutrinos to arrive at their huge lead detector each year only one or two will interact with the nuclei in it.