Cosmic tau neutrino detection via Cherenkov signals from air showers from Earth-emerging taus

Abstract

We perform a new, detailed calculation of the flux and energy spectrum of Earth-emerging τleptons generated from the interactions of tau neutrinos and antineutrinos in the Earth. A layered model of the Earth is used to describe the variable density profile of the Earth. Different assumptions regarding the neutrino charged-and neutral-current cross sections as well as the τ -lepton energy loss models are used to quantify their contributions to the systematic uncertainty. A baseline simulation is then used to generate the optical Cherenkov signal from upward-moving extensive air showers generated by the τ -lepton decay in the atmosphere, applicable to a range of space-based instruments. We use this simulation to determine the neutrino sensitivity for Eν ∼ > 10 PeV for a space-based experiment with performance similar to that for the Probe of Extreme MultiMessenger Astrophysics (POEMMA) mission currently under study.

Observing EeV neutrinos through Earth: GZK and the anomalous ANITA events

“…[19]. However, in this work we consider neutrino propagation at EeV energies and higher, where this approximation no longer holds and careful treatment of tau energy losses is required; see [40,51] for recent implementations and discussions.…”

“…However, tau neutrinos offer a unique opportunity to detect those neutrinos which prematurely interact in the Earth prior to reaching the detector. When an incident tau neutrino undergoes a charged-current (CC) interaction, the subsequent decay of the produced tau will yield another tau neutrino at a lower energy [34][35][36][37][38][39][40]. Although this process is not unique to the tau channel, the energy distribution of the secondary neutrinos peaks at much higher energies for tau neutrinos than for muon-or electron-neutrinos.…”

Anomalous ANITA air shower events and tau decays

“…We use cumulative distribution functions to sample the energy distribution of the taus that exit for a given incident tau neutrino energy E ντ and angle β tr , as described in detail in Ref. [42].…”

“…A feature unique to tau neutrinos is the significance of tau neutrino regeneration with neutrino interactions in the Earth [42,[55][56][57][58][59][60]. Tau neutrino regeneration comes from tau neutrino charged-current production of taus which subsequently decay back to ν τ .…”

“…Most of the BSM analyses use approximate analytic results and a narrow energy range associated with ANITA's unusual events. In this paper, we consider a range of energies and angles using Monte Carlo simulations of neutral particle interactions that couple to taus, and a stochastic evaluation of tau energy loss in the Earth [42]. Using a simplified model of the ANITA detection probability, we find the angular dependence of the effective aperture.…”