SNO Nus Is Good News; September 2001; Scientific American Magazine; by Graham P. Collins; 2 Page(s)

Tell tale flashes of light within a 1,000-ton sphere of ultrapure heavy water, deep underground in a nickel mine near Sudbury, Ontario, have resolved a 33-yearold puzzle. In June the Sudbury Neutrino Observatory (SNO) collaboration announced firm evidence that elusive ghostly particles called neutrinos morph from one subspecies to another during their flight from the sun to Earth. The result reassures astrophysicists that their precision solar models do not contain a lurking blunder, and it gives particle physicists further clues to what lies beyond their beloved but incomplete Standard Model of particle physics.

The mystery of solar neutrinos has haunted physicists since 1968, when the first experiment to count those neutrinos came up with less than half of the expected number. Three decades of experiments and more refined theories have only confirmed the discrepancy.