Effects of initial spatial phase in radiative neutrino pair emission

We study radiative neutrino pair emission in a deexcitation process of atoms taking into account the coherence effect in a macroscopic target system. In the course of preparing the coherent initial state to enhance the rate, a spatial phase factor is imprinted on the macroscopic target. It is shown that this initial spatial phase changes the kinematics of the radiative neutrino pair emission. We investigate effects of the initial spatial phase in the photon spectrum of the process. It turns out that the initial spatial phase provides us with significant improvements in exploring neutrino physics, such as the Dirac-Majorana distinction and the cosmic neutrino background.