Search for keV-scale sterile neutrinos with the first KATRIN data
M. Aker, D. Batzler, A. Beglarian, J. Behrens, A. Berlev, U. Besserer, B. Bieringer, F. Block, S. Bobien, B. Bornschein, L. Bornschein, M. Böttcher, T. Brunst, T. S. Caldwell, S. Chilingaryan, W. Choi, K. Debowski, M. Descher, D. Díaz Barrero, P. J. Doe, O. Dragoun, G. Drexlin, F. Edzards, K. Eitel, E. Ellinger, R. Engel, S. Enomoto, A. Felden, J. A. Formaggio, F. M. Fränkle, G. Franklin, F. Friedel, A. Fulst, K. Gauda, A. S. Gavin, W. Gil, F. Glück, R. Grössle, R. Gumbsheimer, V. Hannen, N. Haußmann, K. Helbing, S. Hickford, R. Hiller, D. Hillesheimer, D. Hinz, T. Höhn, T. Houdy, A. Huber, A. Jansen, C. Karl, J. Kellerer, M. Kleifges, M. Klein, C. Köhler, L. Köllenberger, A. Kopmann, M. Korzeczek, A. Kovalı́k, B. Krasch, H. Krause, L. La Cascio, T. Lasserre, Thanh-Long Le, O. Lebeda, B. Lehnert, A. Lokhov, M. Machatschek, E. Malcherek, Melanie D. Mark, A. Marsteller, E. L. Martín, C. Melzer, S. Mertens, J. Mostafa, K. Müller, H. Neumann, S. Niemes, P. Oelpmann, D. S. Parno, A. W. P. Poon, J.M.L. Poyato, F. Priester, Jan Ráliš, S. Ramachandran, R. G. H. Robertson, Werner Rodejohann, C. Rodenbeck, M. Röllig, C. Röttele, M. Ryšavý, R. Sack, Alejandro Sáenz, R. Salomon, P. Schäfer, L. Schimpf, Magnus Schlösser, K. Schlösser, L. Schlüter, S. Schneidewind
Abstract
Abstract In this work we present a keV-scale sterile-neutrino search with a low-tritium-activity data set of the KATRIN experiment, acquired in a commissioning run in 2018. KATRIN performs a spectroscopic measurement of the tritium $$\upbeta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>β</mml:mi> </mml:math> -decay spectrum with the main goal of directly determining the effective electron anti-neutrino mass. During this commissioning phase a lower tritium activity facilitated the measurement of a wider part of the tritium spectrum and thus the search for sterile neutrinos with a mass of up to $$1.6\, \textrm{keV}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>1.6</mml:mn> <mml:mspace/> <mml:mtext>keV</mml:mtext> </mml:mrow> </mml:math> . We do not find a signal and set an exclusion limit on the sterile-to-active mixing amplitude of $$\sin ^2\theta < 5\times 10^{-4}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mo>sin</mml:mo> <mml:mn>2</mml:mn> </mml:msup> <mml:mi>θ</mml:mi> <mml:mo><</mml:mo> <mml:mn>5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ( $$95\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>95</mml:mn> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> C.L.) at a mass of 0.3 keV. This result improves current laboratory-based bounds in the sterile-neutrino mass range between 0.1 and 1.0 keV.