First direct neutrino-mass measurement with sub-eV sensitivity

• Published in: arXiv.org 2021-05
• Main Authors: Beglarian, A, Behrens, J, Berlev, A, Besserer, U, Bieringer, B, Bornschein, B, Bornschein, L, Böttcher, M, Brunst, T, Caldwell, T S, Carney, R M D, La Cascio, L, Chilingaryan, S, Choi, W, Debowski, K, Descher, M, D Díaz Barrero, Doe, P J, Drexlin, G, Eitel, K, Ellinger, E, Engel, R, Enomoto, S, maggio, J A, Fränkle, F M, Franklin, G B, Friedel, F, Fulst, A, Gauda, K, Gil, W, Glück, F, Grössle, R, Gupta, V, Höhn, T, Haußmann, N, Hickford, S, Hiller, R, Hillesheimer, D, Hinz, D, Huber, A, Jansen, A, Kellerer, F, Kellerer, J, Klein, M, Köhler, C, Köllenberger, L, Kopmann, A, Korzeczek, M, Kovalík, A, Krasch, B, Krause, H, Kunka, N, Lasserre, T, Le, T L, Lehnert, B, Lokhov, A, Machatschek, M, Malcherek, E, Mark, M, Martin, E L, Melzer, C, Menshikov, A, Mertens, S, Mostafa, J, Müller, K, Niemes, S, Oelpmann, P, Parno, D S, Poon, A W P, Poyato, J M L, Röttele, C, Rodejohann, W, Rodenbeck, C, Sack, R, Schaller, A, Schlösser, K, Schlösser, M, Schneidewind, S, Schrank, M, Schulz, B, Schwemmer, A, Šefčík, M, Sibille, V, Slezák, M, Steidl, M, Sun, M, Telle, H H, Thorne, L A, Thümmler, T, Tkachev, I, Urban, K, Valerius, K, Vizcaya Hernández, A P, Wendel, J, Wilkerson, J F, Wüstling, S, W Xu, Y -R Yen, Zadoroghny, S, Zeller, G
• Format: Article
• Language: English
• Subjects: Beta decay; Confidence intervals; Neutrinos; Sensitivity; Tritium
• ISSN: 2331-8422

We report the results of the second measurement campaign of the Karlsruhe Tritium Neutrino (KATRIN) experiment. KATRIN probes the effective electron anti-neutrino mass, \(m_{\nu}\), via a high-precision measurement of the tritium \(\beta\)-decay spectrum close to its endpoint at \(18.6\,\mathrm{keV}\). In the second physics run presented here, the source activity was increased by a factor of 3.8 and the background was reduced by \(25\,\%\) with respect to the first campaign. A sensitivity on \(m_{\nu}\) of \(0.7\,\mathrm{eV/c^2}\) at \(90\,\%\) confidence level (CL) was reached. This is the first sub-eV sensitivity from a direct neutrino-mass experiment. The best fit to the spectral data yields \(m_{\nu}^2 = (0.26\pm0.34)\,\mathrm{eV^4/c^4}\), resulting in an upper limit of \(m_{\nu}