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HK: Fachverband Physik der Hadronen und Kerne

HK 20: Astroparticle Physics II

HK 20.3: Vortrag

Dienstag, 12. März 2024, 16:30–16:45, HBR 19: C 103

Measurement of the nuclear transition energies of ^83mKr using the gaseous krypton source of KATRIN — •Matthias Böttcher and Benedikt Bieringer for the KATRIN collaboration — Institut für Kernphysik, Universität Münster

The KATRIN experiment aims to measure the electron neutrino mass m_ν with 0.3 eV/c² (90% C.L.) sensitivity after 1000 measurement days in 2025, by measuring the Tr beta spectrum near its endpoint E₀, and performing a fit including parameters E₀ and m_ν². Since these are highly correlated, systematic effects influencing the obtained m_ν will also manifest in E₀ and the derived Tr Q value. The latter is therefore valuable for cross checks of our experimental procedure. The KATRIN Q value can be determined by absolute calibration with ^83mKr conversion electron lines. This is limited by knowledge of ^83mKr nuclear transition energies, being known to 0.3 eV precision in literature. The excited nucleus of ^83mKr decays via two-step cascade of 32.2 keV and 9.4 keV highly converted gamma transitions, and a suppressed direct transition. Using a gaseous Kr source at KATRIN, a new measurement of conversion electron lines from all three transitions was performed in 2023. Following the method described in ref. EPJ C 82 (2022) 700, the nuclear transition energies can be determined, which can allow for a reduction of the Tr Q value uncertainty to below 0.1 eV. In this talk the result of the new measurement is presented. This work is supported by Helmholtz Association and Ministry for Education and Research BMBF (grant numbers 05A23PMA, 05A23PX2, 05A23VK2, and 05A23WO6).

Keywords: Neutrino mass; Krypton; Conversion electrons; KATRIN; Q value