Combined neutrino-mass analysis of the first five KATRIN science runs

The observation of neutrino oscillation proved that neutrinos possess a non-zero mass.
Neutrinos are one of the most elusive particles, the absolute mass scale of neutrinos remains unknown until today. The KArlsruhe TRItium Neutrino (KATRIN) collaboration aims to measure the neutrino mass by precision spectroscopy of tritium $\beta$-decay with a design sensitivity of 0.2 eV/c$^2$. To this end, KATRIN measures the endpoint region of the tritium $\beta$-electron spectrum. The first science run was taken in Spring 2019. Since then, more measurement campaigns have further improved the statistical precision. With an increasing number of campaigns, a combined analysis of all collected data becomes more challenging.

The main work presented in this thesis focuses on the neutrino-mass analysis of the first five neutrino-mass measurement campaigns. This result improves on previous neutrino mass limits from kinematic measurements.

Probing the neutrino mass is the main purpose of the KATRIN experiment.
Beyond this, the ultra-precise measurement of the $\beta$-spectrum can be used for new physics searches. One such study is the search for extra (sterile) neutrino states.
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The result of the light sterile neutrino search at the eV mass scale is presented based on the first and second KATRIN measurement campaigns.