Prospects for cosmic neutrino detection in tritium experiments in the case of hierarchical neutrino masses

TL;DR

This paper evaluates the potential for detecting the cosmic neutrino background using future tritium decay experiments, emphasizing the importance of energy resolution and neutrino mass hierarchy.

Contribution

It analyzes how neutrino mixing and mass hierarchy affect CNB detection prospects in upcoming tritium experiments, highlighting necessary technological improvements.

Findings

Detection possible with improved energy resolution for inverted hierarchy

Normal hierarchy detection requires even better resolution

Mixing effects reduce detection prospects due to background increase

Abstract

We discuss the effects of neutrino mixing and the neutrino mass hierarchy when considering the capture of the cosmic neutrino background (CNB) on radioactive nuclei. The implications of mixing and hierarchy at future generations of tritium decay experiments are considered. We find that the CNB should be detectable at these experiments provided that the resolution for the kinetic energy of the outgoing electron can be pushed to a few 0.01 eV for the scenario with inverted neutrino mass hierarchy, about an order of magnitude better than that of the upcoming KATRIN experiment. Another order of magnitude improvement is needed in the case of normal neutrino mass hierarchy. We also note that mixing effects generally make the prospects for CNB detection worse due to an increased maximum energy of the normal beta decay background.