Results from KATRIN - First direct neutrino-mass measurement with sub-eV sensitivity*

Determining the absolute neutrino-mass scale of neutrinos is vital to our understanding of fundamental interactions and the origin of particle masses, as well as to cosmology and astrophysics. The Karlsruhe Tritium Neutrino (KATRIN) experiment probes the effective electron anti-neutrino mass (m_ν) via a high precision kinematics measurement of the tritium beta-decay spectrum close to its endpoint at 18.6 keV.  Such direct kinematic measurements are complementary to cosmological based observations and neutrinoless double beta decay searches with the advantage that they are independent of the nature of the neutrino (Majorana or Dirac) and to cosmological model assumptions. KATRIN has recently achieved the first sub-eV sensitivity from a direct neutrino mass experiment with a sensitivity on m_ν of 0.7 eV/c² at 90% confidence level (CL). The best fit to the spectral data yields m²_ν = (0.26 ± 0.34) eV²/c⁴, resulting in an upper limit of m_ν < 0.9 eV/c² (90 % CL). By combining this result with KATRIN's first neutrino mass campaign, we set an upper limit of m_ν < 0.8 eV/c² (90 % CL).