Revisiting the origin of neutrino flavor transformations

Abstract

To account for neutrino oscillations, it was postulated that the neutrino has nonvanishing mass and each flavor eigenstate is formed by a quantum superposition of three distinct mass eigenstates, whose probability amplitudes interfere with each other during its propagation. However, I find that a neutrino or antineutrino produced by the decay of an unstable particle cannot be in such a superposition, as different mass eigenstates, if they exist, are necessarily correlated with different momentum states of the composite system produced by the decay, which would destroy the quantum coherence among these mass eigenstates. I further find that the states of a neutrino and an electron become nonseparable after their charged-current interaction. This nonseparability leads to decoherence for neutrinos propagating in matter, but was not taken into consideration in previous investigations of the matter effect. Due to this decoherence, the deficit of solar electron neutrinos cannot exceed 1/2 based on the aforementioned postulation even if the corresponding superposition of mass eigenstates can be produced. These results unambiguously show that the origin of neutrino flavor transformations needs to be revisited. I propose an alternative mechanism that can reasonably account for neutrino transformations. It is based on virtual excitation of the Z bosonic field diffusing over the space. During the propagation, the neutrino can continually excite and then immediately re-absorb a virtual Z boson. This virtual bosonic excitation produces a backaction on the neutrino, enabling it to oscillate among three flavors. When the neutrino propagates in matter, its behavior is determined by the competition between the coherent flavor transformation and decoherence effect resulting from scatterings.