Reactor data hint at existence of fourth neutrino
Deficit in antiparticle output exceeds theoretical expectations
GHOST FINDER New results of experiments at the Daya Bay neutrino detector (walls lined with photomultiplier tubes, shown) hint at the existence of a lightweight sterile neutrino, about one-millionth the mass of an electron.
Brookhaven National Laboratory/Flickr (CC BY-NC-ND 2.0)
In tunnels deep inside a granite mountain at Daya Bay, a nuclear reactor facility some 55 kilometers from Hong Kong, sensitive detectors are hinting at the existence of a new form of neutrino, one of nature’s most ghostly and abundant elementary particles.
Neutrinos, electrically neutral particles that sense only gravity and the weak nuclear force, interact so feebly with matter that 100 trillion zip unimpeded through your body every second. They come in three known types: electron, muon and tau. The Daya Bay results suggest the possibility that a fourth, even more ghostly type of neutrino exists — one more than physicists’ standard theory allows.
Dubbed the sterile neutrino, this phantom particle would carry no charge of any kind and would be impervious to all forces other than gravity. Only when shedding its invisibility cloak by transforming into an electron, muon or tau neutrino could the sterile neutrino be detected. Definitive evidence &ldquo
