Search for keV-scale Sterile Neutrinos with first KATRIN Data

TL;DR

This study uses initial KATRIN data to search for keV-scale sterile neutrinos, setting new exclusion limits and improving constraints in the 0.1 to 1.0 keV mass range.

Contribution

First search for keV-scale sterile neutrinos using KATRIN's initial data, providing improved laboratory bounds in the 0.1 to 1.0 keV mass range.

Findings

No sterile neutrino signal detected

Set exclusion limits on sterile-to-active mixing amplitude

Improved constraints over previous laboratory bounds

Abstract

In this work we present a keV-scale sterile-neutrino search with the first tritium data of the KATRIN experiment, acquired in the commissioning run in 2018. KATRIN performs a spectroscopic measurement of the tritium $\beta$-decay spectrum with the main goal of directly determining the effective electron anti-neutrino mass. During this commissioning phase a lower tritium activity facilitated the search for sterile neutrinos with a mass of up to $1.6\, \mathrm{keV}$. We do not find a signal and set an exclusion limit on the sterile-to-active mixing amplitude of down to $\sin^2\theta < 5\cdot10^{-4}$ ($95\,\%$ C.L.), improving current laboratory-based bounds in the sterile-neutrino mass range between 0.1 and $1.0\, \mathrm{keV}$.