Improved analysis methods for the determination of the energy-loss function of electrons in high-purity tritium gas at KATRIN

The Karlsruhe Tritium Neutrino Experiment (KATRIN) aims to directly assess the absolute neutrino-mass scale via precision spectroscopy of the tritium beta-decay spectrum in its endpoint region. Energy-losses of electrons scattering with gas molecules while travelling through the high-density gaseous tritium source lead to distortions of the measured energy spectrum and therefore need to be known with high precision. In 2022 and 2023, new measurements of the energy-loss of electrons in tritium gas at different electron energies have been performed with a newly installed high-rate photoelectron source with narrow energy and angular distribution. Those measurements extend earlier measurements at KATRIN which were published in EPJC 81, 579 (2021). In this talk, improved analysis methods developed for the analysis of the new energy-loss data will be presented. This work is supported by the Helmholtz Association, by the Ministry for Education and Research BMBF, by Deutsche Forschungsgemeinschaft DFG (Research Training Group GRK 2149) and other agencies (grant numbers 05A23PMA, 05A23PX2, 05A23VK2, and 05A23WO6).