In the standard treatment of particle oscillations the mass eigenstates are
implicitly assumed to be scalars and, consequently, the spinorial form of
neutrino wave functions is not included in the calculations. To analyze this
additional effect, we discuss the oscillation probability formula obtained by
using the Dirac equation as evolution equation for the neutrino mass
eigenstates. The initial localization of the spinor state also implies an
interference between positive and negative energy components of mass eigenstate
wave packets which modifies the standard oscillation probability.Comment: 14 pages, 1 figure, AMS-Te