The traditional recipe for neutrino detection calls for a very large detector to compensate for the neutral particles’ extraordinarily meager rate of interaction. Yet theory has long offered a means of spotting neutrinos in a much smaller volume. In 1974 Daniel Freedman proposed measuring a low-energy neutrino’s interaction with an entire atomic nucleus. The probability that a neutrino would exchange a Z boson with a nucleus and in the process provide a subtle kick would roughly scale with the square of the nucleus’s neutron count. But there was a catch: The heavy nuclei that would maximize the interaction rate would also barely budge when struck by a feeble neutrino, so their recoil would be difficult to spot.
Researchers with the COHERENT collaboration have now overcome that challenge and measured the neutrino-induced recoils of nuclei in a 15 kg detector, a prototype of which is shown in the photo. They placed...
