Search Capability for $\eta \to \nu_{e,{\tau}}\bar\nu_{e,{\tau}}$ Decays in Cubic Kilometer Neutrino Detectors

TL;DR

This paper explores the potential of cubic kilometer neutrino detectors like IceCube to detect or set limits on forbidden eta meson decays into neutrino pairs, analyzing cascade event signatures and background sources.

Contribution

It presents a novel method to constrain forbidden eta decays using neutrino observatories, providing the first estimates of upper limits on these decay branching ratios.

Findings

Potential to set a branching ratio limit of 4.5×10⁻⁴ at 90% CL

Identification of cascade signatures from eta decays in neutrino detectors

Analysis of atmospheric background contributions to cascade events

Abstract

We investigate the discovery potential of cubic kilometer neutrino observatories such as IceCube to set stringent limits on the forbidden decays $\eta\to\nu_e\bar\nu_e$ and $\eta\to\nu_{\tau}\bar\nu_{\tau}$. The signatures for these decays are cascade events resulting from the charged-current reactions of $\nu_e, \nu_{\tau}$, $\bar\nu_e$ and $\bar\nu_{\tau}$ on nuclei in such detectors. Background cascade events are mainly due to $\nu_e$'s from atmospheric $\mu$, $K^+$, and $K^{0}_S$ decays and to a lesser extent from atmospheric $\nu_{\mu}$ neutral current interactions with nuclei. A direct upper limit for the branching ratio $\eta \to \nu_{e,\tau} \bar\nu_{e,\tau}$ of $4.5\times10^{-4}$ at 90% CL can be achieved.