Direct neutrino-mass measurement with sub-electronvolt sensitivity

M. Aker, A. Beglarian, J. Behrens, A. Berlev, U. Besserer, B. Bieringer, F. Block, S. Bobien, M. Böttcher, B. Bornschein, L. Bornschein, T. Brunst, T. S. Caldwell, R. M. D. Carney, L. La Cascio, S. Chilingaryan, W. Choi, K. Debowski, M. Deffert, M. Descher, D. Díaz Barrero, P. J. Doe, O. Dragoun, G. Drexlin, K. Eitel, E. Ellinger, R. Engel, S. Enomoto, A. Felden, J. A. Formaggio, F. M. Fränkle, G. B. Franklin, F. Friedel, A. Fulst, K. Gauda, W. Gil, F. Glück, R. Grössle, R. Gumbsheimer, V. Gupta, T. Höhn, V. Hannen, N. Haußmann, K. Helbing, S. Hickford, R. Hiller, D. Hillesheimer, D. Hinz, T. Houdy, A. Huber, A. Jansen, C. Karl, F. Kellerer, J. Kellerer, M. Kleifges, M. Klein, C. Köhler, L. Köllenberger, A. Kopmann, M. Korzeczek, A. Kovalík, B. Krasch, H. Krause, N. Kunka, T. Lasserre, T. L. Le, O. Lebeda, B. Lehnert, A. Lokhov, M. Machatschek, E. Malcherek, M. Mark, A. Marsteller, E. L. Martin, C. Melzer, A. Menshikov, 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, S. Ramachandran, R. G. H. Robertson, W. Rodejohann, M. Röllig, C. Röttele, C. Rodenbeck, M. Ryšavý, R. Sack, A. Saenz, P. Schäfer, A. Schaller née Pollithy, L. Schimpf, K. Schlösser, M. Schlösser, L. Schlüter, S. Schneidewind, M. Schrank, B. Schulz, A. Schwemmer, M. Šefčík, V. Sibille, D. Siegmann, M. Slezák, F. Spanier, M. Steidl, M. Sturm, M. Sun, D. Tcherniakhovski, H. H. Telle, L. A. Thorne, T. Thümmler, N. Titov, I. Tkachev, K. Urban, K. Valerius, D. Vénos, A. P. Vizcaya Hernández, C. Weinheimer, S. Welte, J. Wendel, J. F. Wilkerson, J. Wolf, S. Wüstling, J. Wydra, W. Xu, Y.-R. Yen, S. Zadoroghny & G. Zeller

Abstract

Since the discovery of neutrino oscillations, we know that neutrinos have non-zero mass. However, the absolute neutrino-massscale remains unknown. Here we report the upper limits on effective electron anti-neutrino mass, mν, from the second physicsrun of the Karlsruhe Tritium Neutrino experiment. In this experiment, mν is probed via a high-precision measurement ofthe tritium β-decay spectrum close to its endpoint. This method is independent of any cosmological model and does not relyon assumptions whether the neutrino is a Dirac or Majorana particle. By increasing the source activity and reducing the backgroundwith respect to the first physics campaign, we reached a sensitivity on mν of 0.7 eV c–2 at a 90% confidence level (CL).The best fit to the spectral data yields m2ν= (0.26 0.34) eV2 c–4, resulting in an upper limit of mν < 0.9 eV c–2 at 90% CL. Bycombining this result with the first neutrino-mass campaign, we find an upper limit of mν < 0.8 eV c–2 at 90% CL.