UHE tau neutrino flux regeneration while skimming the Earth

TL;DR

This paper investigates how tau neutrino regeneration affects the flux of tau leptons emerging from Earth, which is crucial for detecting ultra-high energy cosmic neutrinos via Earth-skimming methods.

Contribution

It provides a detailed solution to the transport equations for tau neutrino propagation, including regeneration effects, and compares results with and without regeneration under various scenarios.

Findings

Regeneration significantly impacts tau lepton flux predictions.

Neglecting regeneration can lead to inaccurate flux estimates.

The validity of ignoring regeneration depends on cross-section and energy loss models.

Abstract

The detection of Earth-skimming tau neutrinos has turned into a very promising strategy for the observation of ultra-high energy cosmic neutrinos. The sensitivity of this channel crucially depends on the parameters of the propagation of the tau neutrinos through the terrestrial crust, which governs the flux of emerging tau leptons that can be detected. One of the characteristics of this propagation is the possibility of regeneration through multiple $\nu_\tau \leftrightarrow \tau$ conversions, which are often neglected in the standard picture. In this paper, we solve the transport equations governing the $\nu_\tau$ propagation and compare the flux of emerging tau leptons obtained allowing regeneration or not. We discuss the validity of the approximation of neglecting the $\nu_\tau$ regeneration using different scenarios for the neutrino-nucleon cross-sections and the tau energy losses.