We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0_{-1.1}^{+0.9}) eV^{2}. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation.

Center for Experimental Nuclear Physics and Astrophysics and Department of Physics University of Washington Seattle Washington 98195 USA

Departamento de Química Física Aplicada Universidad Autonoma de Madrid Campus de Cantoblanco 28049 Madrid Spain

Department of Physics and Astronomy University of North Carolina Chapel Hill North Carolina 27599 USA

Department of Physics Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA

Department of Physics Case Western Reserve University Cleveland Ohio 44106 USA

Department of Physics Faculty of Mathematics and Natural Sciences University of Wuppertal Gaußstraße 20 42119 Wuppertal Germany

Helmholtz Institut für Strahlen und Kernphysik Rheinische Friedrich Wilhelms Universität Bonn Nussallee 14 16 53115 Bonn Germany

Institut für Kernphysik Westfälische Wilhelms Universität Münster Wilhelm Klemm Straße 9 48149 Münster Germany

Institut für Physik Humboldt Universität zu Berlin Newtonstraße 15 12489 Berlin Germany

Institut für Physik Johannes Gutenberg Universität Mainz 55099 Mainz Germany

Institute for Data Processing and Electronics Hermann von Helmholtz Platz 1 76344 Eggenstein Leopoldshafen Germany

Institute for Nuclear and Particle Astrophysics and Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA

Institute for Nuclear Physics Hermann von Helmholtz Platz 1 76344 Eggenstein Leopoldshafen Germany

Institute for Nuclear Research of Russian Academy of Sciences 60th October Anniversary Prospect 7a 117312 Moscow Russia

Institute for Technical Physics Hermann von Helmholtz Platz 1 76344 Eggenstein Leopoldshafen Germany

Institute of Experimental Particle Physics Wolfgang Gaede Straße 1 76131 Karlsruhe Germany

IRFU CEA Université Paris Saclay 91191 Gif sur Yvette France

Laboratory for Nuclear Science Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge Massachusetts 02139 USA

Max Planck Institut für Kernphysik Saupfercheckweg 1 69117 Heidelberg Germany

Max Planck Institut für Physik Föhringer Ring 6 80805 München Germany

Nuclear Physics Institute of the CAS v v i CZ 250 68 Řež Czech Republic

Project Process and Quality Management Hermann von Helmholtz Platz 1 76344 Eggenstein Leopoldshafen Germany

Technische Universität München James Franck Straße 1 85748 Garching Germany

Triangle Universities Nuclear Laboratory Durham North Carolina 27708 USA

University of Applied Sciences Fulda Leipziger Straße 123 36037 Fulda Germany

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