A new contribution to the conventional atmospheric neutrino flux

TL;DR

This paper calculates the contribution of $K_S$ semileptonic decay to the high-energy atmospheric $ u_e$ flux, revealing a significant increase above 100 TeV and establishing relations among kaon decay channels.

Contribution

It provides the first detailed calculation of $K_S$ decay contribution to atmospheric $ u_e$ flux at high energies, highlighting its significance.

Findings

$K_S$ decay increases $ u_e$ flux by ~30% above 100 TeV

$ u_e$ fluxes from $K^+$, $K_L$, and $K_S$ are nearly equal at high energies

High critical energy of $K_S$ enhances its decay contribution at TeV energies

Abstract

Atmospheric neutrinos are an important background to astrophysical neutrino searches, and are also of considerable interest in their own right. This paper points out that the contribution to conventional atmospheric $\nu_e$ of the rare semileptonic decay of $K_S$ becomes significant at high energy. Although the $K_S\rightarrow \pi e\nu$ branching ratio is very small, the short $K_S$ lifetime leads to a high critical energy, so that, for vertical showers, the inclusion of $K_S$ semileptonic decay increases the conventional $\nu_e$ flux by $\approx 30%$ at energies above 100 TeV. In this paper, we present calculations of the flux of $\nu_e$ from $K_S$. At energies above their critical energies, the $\nu_e$ fluxes from kaon decay may be simply related to the kaon semileptonic widths; this leads to a near-equality between the flux of $\nu_e$ from $K^+$, $K_L$ and $K_S$.