WAY TO DISTINGUISH BETWEEN MAJORANA AND DIRAC MASSIVE NEUTRINOS IN NEUTRINO-COUNTING REACTIONS

The question of ascertaining the Majorana and Dirac nature of heavy fourth-generation or excited neutrinos is considered model independently without assuming definite handedness. Expressions for longitudinal- and transverse-polarization asymmetries in the reaction e+e---> NN-gammaBAR are given in the cases when N is a Majorana or Dirac neutrino. Measurements of such asymmetries provide a way to ascertain the nature of neutrinos. For different masses of neutrinos, numerical computation of longitudinal-polarization asymmetries at definite emission angles of the photon and neutrino and at definite neutrino energy are performed. Significant differences in the cases when final neutrinos are Majorana or Dirac are observed.