Neutrino pair annihilation above black-hole accretion disks in modified gravity

Abstract

Using idealized models of the accretion disk, we investigate the effects induced by the modified theories of gravity on the annihilation of the neutrino pair annihilation into electron-positron pairs ($\nu{\bar \nu}\to e^-e^+$), occurring near the rotational axis. For the accretion disk, we have considered the models with temperature $T=constant$ and $T\propto r^{-1}$. In both cases, we find that the modified theories of gravity lead to an enhancement, up to more than one order of magnitude with respect to General Relativity, of the rate of the energy deposition rate of neutrino pair annihilation.