Improved eV-scale Sterile-Neutrino Constraints from the Second KATRIN Measurement Campaign
Creators: name: Aker, M.
name: Batzler, D.
name: Beglarian, A.
name: Behrens, J.
name: Berlev, A.
name: Besserer, U.
name: Bieringer, B.
name: Block, F.
name: Bobien, S.
name: Bornschein, B.
name: Bornschein, L.
name: Böttcher, M.
name: Brunst, T.
name: Caldwell, T. S.
name: Carney, R. M. D.
name: Chilingaryan, S.
name: Choi, W.
name: Debowski, K.
name: Descher, M.
name: Barrero, D. Díaz
name: Doe, P. J.
name: Dragoun, O.
name: Drexlin, G.
name: Edzards, F.
name: Eitel, K.
name: Ellinger, E.
name: Engel, R.
name: Enomoto, S.
name: Felden, A.
name: Formaggio, J. A.
name: Fränkle, F. M.
name: Franklin, G. B.
name: Friedel, F.
name: Fulst, A.
name: Gauda, K.
name: Gavin, A. S.
name: Gil, W.
name: Glück, F.
name: Grössle, R.
name: Gumbsheimer, R.
name: Hannen, V.
name: Haußmann, N.
name: Helbing, K.
name: Hickford, S.
name: Hiller, R.
name: Hillesheimer, D.
name: Hinz, D.
name: Höhn, T.
name: Houdy, T.
name: Huber, A.
name: Jansen, A.
name: Karl, C.
name: Kellerer, J.
name: Kleifges, M.
name: Klein, M.
name: Köhler, C.
name: Köllenberger, L.
name: Kopmann, A.
name: Korzeczek, M.
name: Kovalík, A.
name: Krasch, B.
name: Krause, H.
name: La Cascio, L.
name: Lasserre, T.
name: Le, T. L.
name: Lebeda, O.
name: Lehnert, B.
name: Lokhov, A.
name: Machatschek, M.
name: Malcherek, E.
name: Mark, M.
name: Marsteller, A.
name: Martin, E. L.
name: Melzer, C.
name: Mertens, S.
name: Mostafa, J.
name: Müller, K.
name: Neumann, H.
name: Niemes, S.
name: Oelpmann, P.
name: Parno, D. S.
name: Poon, A. W. P.
name: Poyato, J. M. L.
name: Priester, F.
name: Ráliš, J.
name: Ramachandran, S.
name: Robertson, R. G. H.
name: Rodejohann, W.
name: Rodenbeck, C.
name: Röllig, M.
name: Röttele, C.
name: Ryšavý, M.
name: Sack, R.
name: Saenz, A.
name: Salomon, R.
name: Schäfer, P.
name: Schimpf, L.
name: Schlösser, M.
name: Schlösser, K.
name: Schlüter, L.
name: Schneidewind, S.
name: Schrank, M.
name: Schwemmer, A.
name: Šefčík, M.
name: Sibille, V.
name: Siegmann, D.
name: Slezák, M.
name: Spanier, F.
name: Steidl, M.
name: Sturm, M.
name: Telle, H. H.
name: Thorne, L. A.
name: Thümmler, T.
name: Titov, N.
name: Tkachev, I.
name: Urban, K.
name: Valerius, K.
name: Vénos, D.
name: Hernández, A. P. Vizcaya
name: Weinheimer, C.
name: Welte, S.
name: Wendel, J.
name: Wetter, M.
name: Wiesinger, C.
name: Wilkerson, J. F.
name: Wolf, J.
name: Wüstling, S.
name: Wydra, J.
name: Xu, W.
name: Zadoroghny, S.
name: Zeller, G.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present the results of the light sterile neutrino search from the second KATRIN measurement campaign in 2019. Approaching nominal activity, $3.76 \times 10^6$ tritium $β$-electrons are analyzed in an energy window extending down to $40\,$eV below the tritium endpoint at $E_0 = 18.57\,$keV. We consider the $3ν+1$ framework with three active and one sterile neutrino flavor. The analysis is sensitive to a fourth mass eigenstate $m_4^2\lesssim1600\,$eV$^2$ and active-to-sterile mixing $|U_{e4}|^2 \gtrsim 6 \times 10^{-3}$. As no sterile-neutrino signal was observed, we provide improved exclusion contours on $m_4^2$ and $|U_{e4}|^2$ at $95\,$% C.L. Our results supersede the limits from the Mainz and Troitsk experiments. Furthermore, we are able to exclude the large $Δm_{41}^2$ solutions of the reactor antineutrino and gallium anomalies to a great extent. The latter has recently been reaffirmed by the BEST collaboration and could be explained by a sterile neutrino with large mixing. While the remaining solutions at small $Δm_{41}^2$ are mostly excluded by short-baseline reactor experiments, KATRIN is the only ongoing laboratory experiment to be sensitive to relevant solutions at large $Δm_{41}^2$ through a robust spectral shape analysis.
description: 14 pages, 8 figures, 2 tables