Testing neutrino instability with active galactic nuclei

Abstract

Active galactic nuclei and gamma ray bursts at cosmological distances are sources of high-energy electron and muon neutrinos and provide a unique test bench for neutrino instability. The typical lifetime-to-mass ratio one can reach there is $\ddot{I}„/m\sim 500Mpc/c{E}_{\hat{I}}½\sim 500$ s/eV. We study the rapid decay channel $\hat{I}{½}_i\to \hat{I}{½}_j+\ddot{I}•$, where $\ddot{I}•$ is a massless or very light scalar (possibly a Goldstone boson), and point out that one can test the coupling strength of $g_{ij}\hat{I}{½}_i\hat{I}{½}_j$ down to $g_{ij}\lsim 10^{-8} eV/m$ by measuring the relative fluxes of $\hat{I}{½}_e$, $\hat{I}{½}_{\hat{I}}¼$ and $\hat{I}{½}_{\ddot{I}}„$. This is orders of magnitude more stringent bound than what one can obtain in other phenomena, e.g. in neutrinoless double beta decay with scalar emission.

3 pages