Unstable Cosmic Neutrino Capture

TL;DR

This paper forecasts how future experiments like PTOLEMY could constrain neutrino lifetimes and properties of invisible decay products by analyzing cosmic neutrino background capture signals.

Contribution

It introduces a method to constrain neutrino decay parameters and invisible particle masses using C$ u$B capture data, including spectral analysis of decay products.

Findings

Forecasts constraints on neutrino lifetime from C$ u$B capture

Formulates energy spectra for decay neutrinos and electrons

Provides a framework for analyzing invisible neutrino decays

Abstract

Future direct observations of the Cosmic Neutrino Background (C$\nu$B) have the potential to explore a neutrino lifetime, especially in the region of the age of the universe, $t_0=4.35\times 10^{17}\ {\rm s}$. We forecast constraints on neutrino decay via capture of the C$\nu$B on tritium, with emphasis on the PTOLEMY-type experiment. In addition, in some cases of invisible neutrino decay into lighter neutrinos in the Standard Model and invisible particles, we can constrain not only the neutrino lifetime but also the masses of the invisible particles. For this purpose, we also formulate the energy spectra of the lighter neutrinos produced by 2-body and 3-body decays, and those of the electrons emitted in the process of the detection of the lighter neutrinos.