 This matrix was introduced in 1962 by Ziro Maki, Masami Nakagawa and Shoichi Sakata, to explain the neutrino oscillations predicted by Bruno Pontecorvo.The Standard Model of particle physics contains three generations or "flavors" of neutrinos, formula_1, formula_2, and formula_3 labeled according to the charged leptons with which they partner in the charged-current weak interaction.These three eigenstates of the weak interaction form a complete, orthonormal basis for the Standard Model neutrino.