  A Majorana type of the neutrino mass matrix induces a class of lepton number
violating processes. Cross sections of these reactions are given in terms of
the neutrino mass matrix element, and a semi-realistic event rate is estimated.
These processes provide mass and mixing parameters not directly accessible by
the neutrino oscillation experiments. If these processes are discovered with a
larger rate than given here, it would imply a new physics of the lepton number
violation not directly related to the Majorana neutrino mass, such as R-parity
violating operators in SUSY models.
