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arXiv · 2509.03423

Improved limit on the effective electron neutrino mass with the ECHo-1k experiment

Fabienne Adam·Felix Ahrens·Luis E. Ardila Perez·Matthias Balzer·Arnulf Barth·Daniel Behrend-Uriarte·Sebastian Berndt·Klaus Blaum·Frederic W. H. Böhm·Martin Braß·Lorenzo Calza·Katerina Chrysalidis·Menno Door·Holger Dorrer·Christoph E. Düllmann·Klaus Eberhardt·Sergey Eliseev·Christian Enss·Pavel Filianin·Andreas Fleischmann·Robert Gartmann·Loredana Gastaldo·Markus Griedel·Alexander Göggelmann·Robert Hammann·Raphael Hasse·Maurits W. Haverkort·Simon Heinze·Daniel Hengstler·Rasmus Jeske·Josef Jochum·Karl Johnston·Nick Karcher·Sebastian Kempf·Tom Kieck·Ulli Köster·Neven Kovac·Nina Kneip·Kathrin Kromer·Federica Mantegazzini·Bruce A. Marsh·Marc Merstof·Timo Muscheid·Martin Neidig·Yuri N. Novikov·Raghav Pandey·Andreas Reifenberger·Daniel Richter·Alexander Rischka·Sebastian Rothe·Oliver Sander·Rima X. Schüssler·Stephan Scholl·Christoph Schweiger·Clemens Velte·Marc Weber·Matthias Wegner·Klaus Wendt·Tom Wickenhäuser
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Abstract

The effective electron neutrino mass can be determined by analyzing the endpoint region of the $^{163}$Ho electron capture spectrum, provided a measurement with high energy resolution and high statistics using calorimetric techniques. Here, the Electron Capture in $^{163}$Ho collaboration, ECHo, presents an analysis of the most precise $^{163}$Ho spectrum currently available, obtained with the ECHo-1k experiment and comprising about 200 million events. A very low background rate of $B=9.1(1.3)\times 10^{-6}$ /eV/pixel/day was achieved allowing for a reliable analysis of the endpoint region. The derived endpoint energy $Q = 2862(4)$ eV is in excellent agreement with the one independently determined via Penning-trap mass spectrometry of $Q=2863.2(6)$ eV [1]. The upper limit of the effective electron neutrino mass is improved by almost a factor 2 compared to the lowest current value [2], reaching $m_{\nu_\mathrm{e}} < 15 $ eV/c${^2}$ (90\% credible interval).

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Fabienne Adam, Felix Ahrens, Luis E. Ardila Perez, Matthias Balzer, Arnulf Barth, Daniel Behrend-Uriarte, Sebastian Berndt, Klaus Blaum, Frederic W. H. Böhm, Martin Braß, Lorenzo Calza, Katerina Chrysalidis, Menno Door, Holger Dorrer, Christoph E. Düllmann, Klaus Eberhardt, Sergey Eliseev, Christian Enss, Pavel Filianin, Andreas Fleischmann, Robert Gartmann, Loredana Gastaldo, Markus Griedel, Alexander Göggelmann, Robert Hammann, Raphael Hasse, Maurits W. Haverkort, Simon Heinze, Daniel Hengstler, Rasmus Jeske, Josef Jochum, Karl Johnston, Nick Karcher, Sebastian Kempf, Tom Kieck, Ulli Köster, Neven Kovac, Nina Kneip, Kathrin Kromer, Federica Mantegazzini, Bruce A. Marsh, Marc Merstof, Timo Muscheid, Martin Neidig, Yuri N. Novikov, Raghav Pandey, Andreas Reifenberger, Daniel Richter, Alexander Rischka, Sebastian Rothe, Oliver Sander, Rima X. Schüssler, Stephan Scholl, Christoph Schweiger, Clemens Velte, Marc Weber, Matthias Wegner, Klaus Wendt, Tom Wickenhäuser. 2025-09-03. Improved limit on the effective electron neutrino mass with the ECHo-1k experiment. https://arxiv.org/abs/2509.03423

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