Relations between energies at the IceCube depth and those at the earth surface

x: Energy at the surface. y: Energy at the IceCube depth	Muon	Tau
x: Energy at the surface. y: Energy at the IceCube depth	Muon Neutrino	Tau Neutrino
x: Energy at the surface. y: Energy at the IceCube depth	Muon Neutrino to Muon	Tau Neutrino to Tau

The "EHE" Neutrino and induced charged leptons such as mu and tau with energies of EeV are main players here.

The Energy Spectra of Neutrinos and Leptons after the propagation.

The upper figurees show the energy flux of leptons/neutrinos expected in the GZK scenario at the IceCube depth (1400m). These are upgoing (left panel) and downgoing (right panel) particles and the intensities have been integrated over solid angle. A main background against the downgoing events, the atmosphecic muons, has very steap energy spectrum, in contrast to hard spectra of the GZK signals, which allows us to reject the backgrounds by setting higher threshold energy like 10 PeV. Moreover, the atmospheric muons are attenuated by the earth and its flux decreses with zenith angle while the attunuation of the GZK mu/taus is not so severe because they are originated in neutrinos.

The lower figure would directly illustrate this situation. It suggests that the GZK mu/tau would dominate over the atmospheric muon background in the space with zenith below 75 degree.

See Our Paper for the detais "Propagation of EHE Leptons in the Earth published in PRD (2004)

The Java-based Ultrah-high Energy Lepton Integral Transporter

The Simualation works described above have been performed by the 100% pure Java codes we had developed. The JULIeT package allowed ones to calculate propagation of EHE neutrinos, muons and taus on an unified scheme. It also has a function of fast Monte-Carlo event generator. The JULIeT web page is here!!