Direct neutrino-mass measurement based on 259 days of KATRIN data
M. Aker, Dominic Batzler, A. Beglarian, J. Behrens, J. Beisenkötter, M. Biassoni, B. Bieringer, Y. Biondi, F. Block, S. Bobien, Matthias Böttcher, B. Bornschein, L. Bornschein, T. S. Caldwell, Marco Carminati, Auttakit Chatrabhuti, S. Chilingaryan, Byron A. Daniel, K. Debowski, M. Descher, D. Díaz Barrero, P. J. Doe, O. Dragoun, Guido Drexlin, F. Edzards, K. Eitel, Enrico Ellinger, R. Engel, S. Enomoto, A. Felden, Caroline Fengler, C. Fiorini, J. A. Formaggio, Christian Forstner, Florian M. Fränkle, K. Gauda, A. S. Gavin, W. Gil, F. Glück, S. Grohmann, Robin Größle, R. Gumbsheimer, Nathanael Gutknecht, V. Hannen, L. Haßelmann, N. Haußmann, K. Helbing, Hanna Henke, S. Heyns, Stephanie Hickford, R. Hiller, D. Hillesheimer, D. Hinz, Thomas Höhn, Anton Huber, A. Jansen, C. Karl, J. Kellerer, Khanchai Khosonthongkee, M. Kleifges, Manuel Klein, J. Kohpeiß, Christoph Köhler, L. Köllenberger, A. Kopmann, Neven Kovač, A. Kovalı́k, Holger Krause, Luisa La Cascio, Thierry Lasserre, J. Lauer, Thanh-Long Le, O. Lebeda, B. Lehnert, Gen Li, A. Lokhov, M. Machatschek, Martin Mark, A. Marsteller, E. L. Martín, C. Melzer, S. Mertens, Shailaja Mohanty, J. Mostafa, Klaus Müller, A. Nava, Holger Neumann, S. Niemes, A. Onillón, D. S. Parno, M. Pavan, Udomsilp Pinsook, A. W. P. Poon, J. M. L. Poyato, S. Pozzi, Florian Priester, Jan Ráliš, S. Ramachandran, R. G. H. Robertson, C. Rodenbeck
Abstract
That neutrinos carry a nonvanishing rest mass is evidence of physics beyond the Standard Model of elementary particles. Their absolute mass holds relevance in fields from particle physics to cosmology. We report on the search for the effective electron antineutrino mass with the KATRIN experiment. KATRIN performs precision spectroscopy of the tritium β-decay close to the kinematic endpoint. On the basis of the first five measurement campaigns, we derived a best-fit value of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>m</mml:mi> <mml:mi>ν</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.15</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> eV 2 , resulting in an upper limit of m ν < 0.45 eV at 90% confidence level. Stemming from 36 million electrons collected in 259 measurement days, a substantial reduction of the background level, and improved systematic uncertainties, this result tightens KATRIN’s previous bound by a factor of almost two.