Introduction to the Neutrino Properties Listings

In the analogous case of quark mixing via the CKM matrix, the smallness of the off-diagonal terms (small mixing angles) permits a “dominant eigenstate” approximation. Previous editions of this Review had assumed that the dominant eigenstate paradigm applies to neutrinos as well. However, the present results of neutrino oscillation searches show that the mixing matrix contains two large mixing angles. We cannot, therefore, associate any particular state |νi〉 with any particular lepton label e, μ or τ . Nevertheless, neutrinos are produced in weak decays with a definite lepton flavor, and are typically detected by the charged current weak interaction again associated with a specific lepton flavor. The Listings for the neutrino mass that follow are separated into the three associated charged-lepton categories. Other properties (mean lifetime, magnetic moment, charge, and charge radius) are no longer separated this way. If needed, the associated lepton flavor is reported in the footnotes.