  Since 2010 IceCube observed around 50 high-energy neutrino events of cosmic
origin above 60 TeV, but the astrophysical sources of these events are still
unknown. We recently proposed high-energy emitting BL Lac (HBL) objects as
candidate emitters of high-energy neutrinos. Assuming a direct proportionality
between high-energy gamma-ray and very-high energy neutrino fluxes, we
calculated the expected neutrino event number in a year for IceCube and the
presently under construction Km3NeT. To give a value of the significance of a
detection we considered also the background for the single sources. To this aim
we derived the through-going muon rate, generated by muon neutrino including
the effect of Earth absorption, the density of the Earth and the cross section
$\nu N$. Applying this calculation both to HBL sources and the atmospherical
neutrino background, we can calculate the expected significance of the
detection by IceCube, showing that our scenario is compatible with a no
detection of HBL.

High Energy Astrophysical Phenomena