Bound on 3+1 Active-Sterile Neutrino Mixing from the First Four-Week Science Run of KATRIN

• Published in: Physical review letters 2021-03, Vol.126 (9), p.091803-091803, Article 091803
• Main Authors: Aker, M, Altenmüller, K, Beglarian, A, Behrens, J, Berlev, A, Besserer, U, Bieringer, B, Blaum, K, Block, F, Bornschein, B, Bornschein, L, Böttcher, M, Brunst, T, Caldwell, T S, La Cascio, L, Chilingaryan, S, Choi, W, Díaz Barrero, D, Debowski, K, Deffert, M, Descher, M, Doe, P J, Dragoun, O, Drexlin, G, Dyba, S, Edzards, F, Eitel, K, Ellinger, E, Engel, R, Enomoto, S, Fedkevych, M, Felden, A, Formaggio, J A, Fränkle, F M, Franklin, G B, Friedel, F, Fulst, A, Gauda, K, Gil, W, Glück, F, Grössle, R, Gumbsheimer, R, Höhn, T, Hannen, V, Haußmann, N, Helbing, K, Hickford, S, Hiller, R, Hillesheimer, D, Hinz, D, Houdy, T, Huber, A, Jansen, A, Köllenberger, L, Karl, C, Kellerer, J, Kippenbrock, L, Klein, M, Kopmann, A, Korzeczek, M, Kovalík, A, Krasch, B, Krause, H, Lasserre, T, Le, T L, Lebeda, O, Le Guennic, N, Lehnert, B, Lokhov, A, Lopez Poyato, J M, Müller, K, Machatschek, M, Malcherek, E, Mark, M, Marsteller, A, Martin, E L, Melzer, C, Mertens, S, Niemes, S, Oelpmann, P, Osipowicz, A, Parno, D S, Poon, A W P, Priester, F, Röllig, M, Röttele, C, Rest, O, Robertson, R G H, Rodenbeck, C, Ryšavý, M, Sack, R, Saenz, A, Schaller, A, Schäfer, P, Schimpf, L, Schlösser, M, Schlösser, K, Schlüter, L, Schrank, M, Schulz, B
• Format: Article
• Language: English
• Subjects: Anomalies; Beta decay; Gallium; High Energy Physics - Experiment; Neutrinos; Nuclear Experiment; Physics; Tritium
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.126.091803

We report on the light sterile neutrino search from the first four-week science run of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are analyzed by a high-resolution MAC-E filter down to 40 eV below the endpoint at 18.57 keV. We consider the framework with three active neutrinos and one sterile neutrino. The analysis is sensitive to the mass, m_{4}, of the fourth mass state for m_{4}^{2}≲1000  eV^{2} and to active-to-sterile neutrino mixing down to |U_{e4}|^{2}≳2×10^{-2}. No significant spectral distortion is observed and exclusion bounds on the sterile mass and mixing are reported. These new limits supersede the Mainz results for m_{4}^{2}≲1000  eV^{2} and improve the Troitsk bound for m_{4}^{2}