We study the geometric phase (GP) in neutrino oscillation for both Dirac and Majorana neutrinos. We apply the kinematic generalization of the GP to quantum open systems that take into account the coupling to a dissipative environment. In the dissipat
ionless case, the GP does not depend on the Majorana angle. It is not the case in the presence of dissipation and hence the GP can serve as a tool determining the type of the Dirac vs the Majorana neutrino.
We analyze the geometric phase in the neutrino oscillation phenomenon, which follows the pion decay pi+ --> mu+ + u_{mu}. Its value pi is consistent with the present-day global analysis of the Standard Model neutrino oscillation parameters, accounti
ng for the nonzero value of theta_13. The impact of the charge-parity (CP) violating phase delta, the neutrinos nature, and the new physics is discussed.
