The electron neutrino has a corresponding antiparticle, the electron antineutrino (ν_e), which differs only in that some of its properties have equal magnitude but opposite sign. One open question of particle physics is whether or not neutrinos and anti-neutrinos are the same particle, in which case it would be a Majorana fermion, or whether they are different particles, in which case they would be Dirac fermions.

Source : Wikipedia

Several experiments are underway at research facilities to try to determine whether neutrinos and anti-neutrinos are in fact the same particle, e.g. GERDA, EXO, and SNO+. (see Wikipedia)

As yet there are no firm results.

Also see : Neutrino massplugin-autotooltip__plain plugin-autotooltip_bigNeutrino mass

New research has found that the neutrino has a non-zero mass - but this requires a modification to the Standard Model of particle physics. The non-zero mass also means that neutrinos cannot travel at light-speed as photons do.

"Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values, but they don't correspond uniquely to the three flavors. A neutrino created with a specific flavor is in an ass…