  We study spin oscillations of neutrinos gravitationally scattered off a
nonrotating black hole (BH). We derive the transition and survival
probabilities of spin oscillations in quadratures when neutrinos interacts with
BH only. The dependence of the probabilities on the impact parameter is
analyzed. Then, we obtain the effective Schr\"{o}dinger equation for neutrino
spin oscillations in neutrino scattering off BH surrounded by background
matter. This equation is solved numerically in the case of a supermassive BH
with a realistic accretion disk. We find that the observed neutrino fluxes can
be reduced almost 20% because of spin oscillations when neutrinos experience
gravitational scattering. The neutrino interaction with an accretion disk
results in the additional asymmetry in the intensities of outgoing fluxes
depending on the neutrino trajectory.

High Energy Physics - Phenomenology;High Energy Astrophysical Phenomena;General Relativity and Quantum Cosmology