Direct neutrino-mass measurement with sub-electronvolt sensitivity

• Published in: Nature physics Vol. 18; no. 2
• Main Authors: Beglarian, A., Behrens, J., Berlev, A., Besserer, U., Bieringer, B., Block, F., Bobien, S., Böttcher, M., Bornschein, L., Brunst, T., Caldwell, T. S., Carney, R. D., La Cascio, L., Chilingaryan, S., Choi, W., Debowski, K., Deffert, M., Díaz Barrero, D., Doe, P. J., Drexlin, G., Eitel, K., Ellinger, E., Engel, R., Enomoto, S., Felden, A., Formaggio, J. A., Fränkle, F. M., Franklin, G. B., Friedel, F., Gauda, K., Glück, F., Grössle, R., Gumbsheimer, R., Gupta, V., Höhn, T., Hannen, V., Haußmann, N., Hickford, S., Hillesheimer, D., Huber, A., Karl, C., Kellerer, F., Kellerer, J., Klein, M., Köllenberger, L., Kopmann, A., Korzeczek, M., Kovalík, A., Krasch, B., Kunka, N., Lasserre, T., Lebeda, O., Lehnert, B., Lokhov, A., Malcherek, E., Mark, M., Marsteller, A., Melzer, C., Mertens, S., Neumann, H., Oelpmann, P., Parno, D. S., Poyato, J. L., Priester, F., Robertson, R. H., Rodejohann, W., Röllig, M., Rodenbeck, C., Ryšavý, M., Sack, R., Schäfer, P., Schaller née Pollithy, A., Schimpf, L., Schlösser, K., Schlösser, M., Schlüter, L., Schneidewind, S., Schrank, M., Schulz, B., Schwemmer, A., Šefčík, M., Sibille, V., Siegmann, D., Steidl, M., Sturm, M., Sun, M., Tcherniakhovski, D., Telle, H. H., Thorne, L. A., Thümmler, T., Titov, N., Urban, K., Valerius, K., Vénos, D., Vizcaya Hernández, A. P., Welte, S., Wendel, J., Wilkerson, J. F., Wüstling, S., Wydra, J.
• Format: Journal Article
• Language: English
• Published: United States Nature Publishing Group (NPG) 14.02.2022
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; neutrino mass; NUCLEAR PHYSICS AND RADIATION PHYSICS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; tritium
• ISSN: 1745-2473; 1745-2481

Since the discovery of neutrino oscillations, we know that neutrinos have non-zero mass. However, the absolute neutrino-mass scale remains unknown. Here we report the upper limits on effective electron anti-neutrino mass, $m_ν$, from the second physics run of the Karlsruhe Tritium Neutrino experiment. In this experiment, $m_ν$ is probed via a high-precision measurement of the tritium β-decay spectrum close to its endpoint. This method is independent of any cosmological model and does not rely on assumptions whether the neutrino is a Dirac or Majorana particle. By increasing the source activity and reducing the background with respect to the first physics campaign, we reached a sensitivity on $m_v$ of ${\text{0.7eV}c^{-2}}$ at a 90% confidence level (CL). The best fit to the spectral data yields $m\frac{2}{v}=\text{(0.26 ± 0.34)eV}^2c^{-4}$, resulting in an upper limit of $m_v{\text{<0.9eV}}c^{-2}$at 90% CL. By combining this result with the first neutrino-mass campaign, we find an upper limit of mν$m_v{\text{<0.8eV}}c^{-2}$ at 90% CL.