Atmospheric lepton fluxes at very high energy

TL;DR

This paper analyzes the sources of atmospheric muons and neutrinos at very high energies, highlighting the significant role of unflavored mesons and electromagnetic processes in muon production.

Contribution

It introduces a detailed comparison of various sources of atmospheric muons and neutrinos, emphasizing the importance of unflavored mesons and photon conversion at ultra-high energies.

Findings

Unflavored mesons can dominate muon production above 10^3 TeV.

Electromagnetic photon conversion is a significant source of atmospheric muons.

Understanding these sources refines background models for astrophysical neutrino detection.

Abstract

The observation of astrophysical neutrinos requires a detailed understanding of the atmospheric neutrino background. Since neutrinos are produced in meson decays together with a charged lepton, important constraints on this background can be obtained from the measurement of the atmospheric muon flux. Muons, however, can also be produced as mu+ mu- pairs by purely electromagnetic processes. We use the Z-moment method to study and compare the contributions to the atmospheric muon and neutrino fluxes from different sources (pi/K decay, charmed and unflavored hadron decay, and photon conversion into a muon pair). We pay special attention to the contribution from unflavored mesons (eta, eta', rho0, omega and phi). These mesons are abundant in air showers, their lifetimes are much shorter than those of charged pions or kaons, and they have decay branching ratios of order 10^-4 into final states containing a muon pair. We show that they may be the dominant source of muons at E_mu >10^3 TeV.