  The problem of excess gamma radiation in the center of galaxy is discussed
assuming that the photon's production is dominated by two kinds of processes,
the first one due to the conventional kinetic mixing term and, secondly, due to
a kinetic mixing term violating the CP symmetry between dark and visible
photons. The CP violation symmetry between dark and visible sectors is not
forbidden and, in principle, could be considered as an additional source of CP
violation. The conversion probability between dark and visible photons is
calculated and compared between both processes. The processes violating CP are
less significant but contribute non-trivially to the excess gamma radiation.
