Today at the European Physical Society meeting in Stockholm,
the international T2K collaboration announced definitive observation of muon
neutrino to electron neutrino transformation. In 2011, the collaboration
announced the first indication of this process, a new type of neutrino
oscillation. At that time, there was
less than a 1% chance that the result could have been due to a statistical
fluctuation. Today, with 3.5 times more data, this transformation is firmly
established. The probability that a random statistical fluctuations alone would
produce the observed excess of electron neutrinos is less than one in a
trillion. Stated in language of
statistics, a statistical fluctuation is ruled out at the 7.5 sigma level; this
is above the 5 sigma threshold particle physicists use to claim discoveries.