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Abstract

We present a generic structure (the layer structure) for decoherence effects
in neutrino oscillations, which includes decoherence from quantum mechanical
and classical uncertainties. The calculation is done by combining the concept
of open quantum system and quantum field theory, forming a structure composed
of phase spaces from microscopic to macroscopic level. Having information loss
at different levels, quantum mechanical uncertainties parameterize decoherence
by an intrinsic mass eigenstate separation effect, while decoherence for
classical uncertainties is typically dominated by a statistical averaging
effect. With the help of the layer structure, we classify the former as state
decoherence (SD) and the latter as phase decoherence (PD), then further
conclude that both SD and PD result from phase wash-out effects of different
phase structures on different layers. Such effects admit for simple numerical
calculations of decoherence for a given width and shape of uncertainties. While
our structure is generic, so are the uncertainties, nonetheless, a few notable
ones are: the wavepacket size of the external particles, the effective
interaction volume at production and detection, the energy reconstruction model
and the neutrino production profile. Furthermore, we estimate the experimental
sensitivities for SD and PD parameterized by the uncertainty parameters, for
reactor neutrinos and decay-at-rest neutrinos, using a traditional rate
measuring method and a novel phase measuring method.