Atmospheric muon fluxes at sub-orbital neutrino detectors

TL;DR

This paper quantifies atmospheric muon fluxes impacting sub-orbital neutrino detectors, aiding in background estimation and understanding muon evolution in extensive air showers.

Contribution

It introduces a semi-analytic method to calculate muon fluxes at sub-orbital detectors, enhancing background modeling for neutrino observations.

Findings

Muon fluxes are significant backgrounds for sub-orbital neutrino detectors.

The method improves understanding of muon content evolution in air showers.

Results help optimize detector pointing strategies.

Abstract

Very-high-energy and ultra-high-energy neutrinos are messengers of energetic sources in the universe. Sub-orbital and satellite-based neutrino telescopes employ detectors of the atmospheric Cherenkov emission from extensive air showers (EASs) generated by charged particles. These Cherenkov detectors can be pointed below or above the Earth's limb. Cherenkov emissions produced from directions below the limb are from upward-going EASs produced in the atmosphere sourced by Earth-skimming neutrinos. When the Cherenkov telescope is pointed slightly above the Earth's limb, signals from EASs are initiated by cosmic ray interactions in the atmosphere. For sub-orbital detectors, muons produced from cosmic rays in the atmosphere can directly hit the Cherenkov telescope. Using a semi-analytic technique with cascade equations for atmospheric particle fluxes, we quantify the atmospheric muon flux that reaches sub-orbital telescopes like Extreme Universe Space Observatory Super Pressure Balloon 2 (EUSO-SPB2). We assess this potential background to the EAS signals. The calculation technique may also provide an understanding of the evolution of the muon content in individual EAS.