Can one measure the Cosmic Neutrino Background?

TL;DR

This paper explores the potential of the KATRIN experiment to detect or set limits on the Cosmic Neutrino Background by measuring electron neutrino capture on tritium, which could reveal early universe information.

Contribution

It analyzes the feasibility of using KATRIN to detect the CNB through neutrino capture, providing a new approach to study the early universe.

Findings

Detection of CNB with KATRIN is currently not feasible.

KATRIN can set an upper limit on local electron neutrino density.

The method involves observing a peak in the electron spectrum above the Q-value.

Abstract

The Cosmic Microwave Background (CMB) yields information about our Universe at around 380 000 years after the Big Bang (BB). Due to the weak interaction of the neutrinos with matter the Cosmic Neutrino Background (CNB) should give information about a much earlier time of our Universe, around one second after the Big Bang. Probably the most promising method to `see' the Cosmic Neutrino Background is the capture of the electron neutrinos from the Background by Tritium, which then decays into 3He and an electron with the energy of the the Q-value = 18.562 keV plus the electron neutrino rest mass. The `KArlsruhe TRItium Neutrino' (KATRIN) experiment, which is in preparation, seems presently the most sensitive proposed method for measuring the electron antineutrino mass. At the same time KATRIN can also look by the reaction: electron neutrino (~1.95 Kelvin) + 3H --> 3He + e- (with the energy Q = 18.6 keV + electron neutrino mass). The capture of the Cosmic Background Neutrinos (CNB) should show in the electron spectrum as a peak by the electron neutrino rest mass above Q. Here the possibility to see the CNB with KATRIN is studied. A detection of the CNB by KATRIN seems not to be possible at the moment. But KATRIN should be able to determine an upper limit for the local electron neutrino density of the CNB.