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Abstract

The refraction index and matter potential depend on neutrino energy and
this dependence has a resonance character associated to the production
of the mediator in the s-channel. For light mediators and light
particles of medium (background) the resonance can be realized at
energies accessible to laboratory experiments. We study properties of
the energy dependence of the potential for different C-asymmetries of
background. Interplay of the background potential and the vacuum term
leads to (i) bump in the oscillation probability in the resonance
region, (ii) dip related to the MSW resonance in the background, (iii)
substantial deviation of the effective Delta m(2) above the resonance
from the low energy value, etc. We considered generation of mixing in
the background. Interactions with background shifts the energy of usual
MSW resonance and produces new MSW resonances. Searches of the
background effects allow us to put bounds on new interactions of
neutrinos and properties of the background. We show that explanation of
the MiniBooNE excess, as the bump due to resonance refraction, is
excluded.