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### Description

KATRIN has recently reported an unrivalled sub-eV direct constraint of the neutrino mass from tritium beta-decay spectrum measurements [1]. Along with the neutrino-mass search, KATRIN has published first results of searching for a fourth (sterile) neutrino with a mass in the eV-range using the precision beta-decay spectra[2],[3].

The fourth neutrino mass-eigenstate introduces an additional branch into the tritium $\beta$-spectrum which manifests as a kink in the model of the differential spectrum. Position and amplitude of this kink correspond to the sterile neutrino mass $m_4$ and effective mixing angle sin$^2(\theta) = |U_{e4}|^{2}$, respectively. In this work sensitivity studies to light sterile neutrinos based on additional science runs and the effect of systematic uncertainties are presented. The analysis region is a two-dimensional parameter space given by $m_4^2<1000$ eV$^2$ and sin$^2(\theta)<5\times 10^{-1}$. A scanning grid with 50$\times$50 points in the ($m_4^2$, sin$^2(\theta)$) plane is chosen and sensitivity contours are calculated within this parameter space. Future strategies for a combined analysis of successive measurement campaigns are discussed.

*References:*

[1] Direct neutrino-mass measurement with sub-electronvolt sensitivity, KATRIN Collaboration, Nature Phys. 18 (2022) 2, 160-166

[2] Bound on 3+1 Active-Sterile Neutrino Mixing from the First Four-Week Science Run of KATRIN, DOI: 10.1103/PhysRevLett.126.091803,(2021), KATRIN Collaboration

[3] Improved eV-scale sterile-neutrino constraints from the second KATRIN measurement campaign, DOI: 10.1103/PhysRevD.105.072004},(2022), KATRIN Collaboration

Category | Particle / Astroparticle / Cosmology (Experiment) |
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