  The minimally extended standard model of particle physics contains three
right handed or sterile neutrinos, coupled to the active ones by a Dirac mass
matrix and mutually by a Majorana mass matrix. In the pseudo-Dirac case, the
Majorana terms are small and maximal mixing of active and sterile states
occurs, which is generally excluded for solar neutrinos. In a "Diracian" limit,
the physical masses become pairwise degenerate and the neutrinos attain a Dirac
signature. Members of a pair do not oscillate mutually so that their mixing can
be undone, and the standard neutrino model follows as a limit. While two
Majorana phases become physical Dirac phases and three extra mass parameters
occur, a better description of data is offered. Oscillation problems are worked
out in vacuum and in matter. With lepton number -1 assigned to the sterile
neutrinos, the model still violates lepton number conservation and allows very
feeble neutrinoless double beta decay. It supports a sterile neutrino
interpretation of Earth-traversing ultra high energy events detected by ANITA.

General Physics