Propagation of extremely high energy leptons in Earth: Implications for their detection by the IceCube neutrino telescope

Abstract

We present the results of numerical calculations on propagation of Extremely-high energy (EHE) neutrinos and charged leptons in the earth for trajectories in all phase space of nadir angles. Our comprehensive calculation has shown that not only the secondary produced muons but also taus survive without decaying in energy range of 10PeV-100PeV with intensity approximately three orders of magnitude lower than the neutrino flux regardless of EHE neutrino production models. They form detectable horizontal or downgoing events in a 1km 3 underground neutrino telescope such as the IceCube detector. The event rate and the resultant detectability of EHE signals in comparison with the atmospheric muon background are also evaluated. The 90 % C.L. upperlimit of EHE neutrino fluxes by a km 2 detection area would be placed at E 2 dF/dE 3.7 × 10 −8 GeV/cm 2 sec sr for ν µ and 4.6 × 10 −8 for ν τ with energies of 10 9 GeV in absence of signals with energy-loss in a detection volume of 10PeV or greater.

Non-standard interactions with high-energy atmospheric neutrinos at IceCube

“…Whereas in the case of ν e 's and ν µ 's, the neutrino flux is absorbed via CC interactions and redistributed (degraded in energy) via NC interactions [84], in the case of ν τ 's, there is another effect. Unlike what happens for ν e and ν µ CC interactions, where charged leptons are quickly brought to rest and do not contribute to the high-energy neutrino flux, the tau leptons produced after ν τ CC interactions can decay before being stopped, so ν τ 's are not absorbed, but the flux gets regenerated (at lower energies) [85][86][87][88][89][90][91]. Thus, for each ν τ which is absorbed via CC interactions, another ν τ with lower energy is produced, and the Earth does not become opaque to high-energy ν τ 's.…”

Differential limit on the extremely-high-energy cosmic neutrino flux in the presence of astrophysical background from nine years of IceCube data

“…[18], which predicted a higher prompt neutrino flux than recent calculations [19], and represent a conservative background estimate. The EHE neutrino-induced events were simulated by the JULIET package [20], which provides the cosmogenic (GZK) signal simulation sample as well as simulations of the astrophysical background events, whose spectrum is assumed to be described by an unbroken power law in the relevant energy region. The detailed simulation procedure used in this work is described in Ref.…”

Ultrahigh energy neutrinos in the Mediterranean: detecting ντand νμwith a km3telescope

“…But the decay length of such a UHE τ is l decay ≃ 50 km ×(E τ /EeV), to be compared with the dimensions of the Auger fiducial volume, ∼ 50 × 60 × 10 km 3 . Conversely, a neutrino telescope can detect taus or muons which are produced very far from the detector by a neutrino charged-current interaction, from distances comparable to the charged lepton range at that particular energy [31]. Indeed, the τ range in water is of the order of several kilometers: from the value of β τ = 0.71 × 10 −6 cm 2 g −1 we obtain an attenuation length 1/(β τ ̺ w ) ≃ 15 km, while for muons (see next section) the range is approximately eight times smaller, of the order of 2 km.…”

“…Although NT's were originally thought as ν µ detectors, their capability as ν τ detectors has become a hot topic [27,28,29,30,31,32,33,34,35], in view of the fact that neutrino oscillations lead to nearly equal astrophysical fluxes for the three neutrino flavors ‡. Despite the different behavior of the produced tau leptons with respect to muons in terms of energy loss and decay length, both ν µ and ν τ detection are sensitive to the matter distribution near the NT site.…”