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Spectral measurement of the ${}^{214}{Bi} β$ decay to the ${}^{214}{Po}$ ground state with the XENONnT Experiment

E. Aprile ¹, J. Aalbers ², K. Abe ³, M. Adrover ⁴, S. Ahmed Maouloud ⁵, L. Althueser ⁶, B. Andrieu ⁵, E. Angelino ⁷, D. Antón Martin ⁸ et al. (XENON Collaboration^¶)

D. Antón Martin ⁸, S. R. Armbruster ⁹, F. Arneodo ¹⁰, L. Baudis ⁴, M. Bazyk ¹¹, L. Bellagamba ¹², R. Biondi ^13,7, A. Bismark ⁴, K. Boese ⁹, R. M. Braun ⁶, A. Brown ¹⁴, G. Bruno ¹¹, R. Budnik ¹³, C. Cai¹⁵, C. Capelli ⁴, J. M. R. Cardoso ¹⁶, A. P. Cimental Chávez ⁴, A. P. Colijn ¹⁷, J. Conrad ¹⁸, J. J. Cuenca-García ⁴, V. D'Andrea ^7,*, L. C. Daniel Garcia ⁵, M. P. Decowski ¹⁷, A. Deisting ¹⁹, C. Di Donato ^20,7, P. Di Gangi ¹², S. Diglio ¹¹, K. Eitel ²¹, S. el Morabit ¹⁷, R. Elleboro²⁰, A. Elykov ²¹, A. D. Ferella ^20,7, C. Ferrari ⁷, H. Fischer ¹⁴, T. Flehmke ¹⁸, M. Flierman ¹⁷, D. Fuchs ¹⁸, W. Fulgione ^22,7, C. Fuselli ^17,†, R. Gaior ⁵, F. Gao ¹⁵, R. Giacomobono ²³, F. Girard ⁵, R. Glade-Beucke ¹⁴, L. Grandi ⁸, J. Grigat ¹⁴, H. Guan ²⁴, M. Guida ⁹, P. Gyorgy ¹⁹, R. Hammann ⁹, A. Higuera ²⁵, C. Hils ¹⁹, L. Hoetzsch ^4,9, N. F. Hood ²⁶, M. Iacovacci ²³, Y. Itow ²⁷, J. Jakob ⁶, F. Joerg ⁴, Y. Kaminaga ³, M. Kara ²¹, S. Kazama ²⁷, P. Kharbanda ¹⁷, M. Kobayashi ²⁷, D. Koke ⁶, K. Kooshkjalali¹⁹, A. Kopec ^26,‡, H. Landsman ¹³, R. F. Lang ²⁴, L. Levinson ¹³, I. Li ²⁵, S. Li ²⁸, S. Liang ²⁵, Z. Liang ²⁸, Y.-T. Lin ^6,9,§, S. Lindemann ¹⁴, M. Lindner ⁹, K. Liu ¹⁵, M. Liu ¹, J. Loizeau ¹¹, F. Lombardi ¹⁹, J. A. M. Lopes ^16,∥, G. M. Lucchetti ¹², T. Luce ¹⁴, Y. Ma ²⁶, C. Macolino ^20,7, J. Mahlstedt ¹⁸, F. Marignetti ²³, T. Marrodán Undagoitia ⁹, K. Martens ³, J. Masbou ¹¹, S. Mastroianni ²³, V. Mazza¹², A. Melchiorre ^20,7, J. Merz ¹⁹, M. Messina ⁷, K. Miuchi ²⁹, A. Molinario ²², S. Moriyama ³, K. Morå ¹, M. Murra ¹, J. Müller ¹⁴, K. Ni ²⁶, C. T. Oba Ishikawa ³, U. Oberlack ¹⁹, S. Ouahada ⁴, B. Paetsch ¹³, Y. Pan ⁵, Q. Pellegrini ⁵, R. Peres ⁴, J. Pienaar ¹³, M. Pierre ¹⁷, G. Plante ¹, T. R. Pollmann ¹⁷, A. Prajapati ²⁰, L. Principe ¹¹, J. Qin ²⁵, D. Ramírez García ⁴, M. Rajado ⁴, A. Ravindran ¹¹, A. Razeto ⁷, R. Singh ²⁴, L. Sanchez ²⁵, J. M. F. dos Santos ¹⁶, I. Sarnoff ¹⁰, G. Sartorelli ¹², J. Schreiner⁹, P. Schulte ⁶, H. Schulze Eißing ⁶, M. Schumann ¹⁴, L. Scotto Lavina ⁵, M. Selvi ¹², F. Semeria ¹², P. Shagin ¹⁹, S. Shi ¹, H. Simgen ⁹, A. Stevens ¹⁴, C. Szyszka ¹⁹, A. Takeda ³, Y. Takeuchi ²⁹, P.-L. Tan ¹, D. Thers ¹¹, G. Trinchero ²², C. D. Tunnell ²⁵, F. Tönnies ¹⁴, K. Valerius ²¹, S. Vecchi ³⁰, S. Vetter ²¹, G. Volta ⁹, C. Weinheimer ⁶, M. Weiss ¹³, D. Wenz ⁶, C. Wittweg ⁴, V. H. S. Wu ²¹, Y. Xing ¹¹, D. Xu ¹, Z. Xu ¹, M. Yamashita ³, J. Yang ²⁸, L. Yang ²⁶, J. Ye ³¹, M. Yoshida ³, L. Yuan ⁸, G. Zavattini ³⁰, Y. Zhao ¹⁵, M. Zhong ²⁶, and T. Zhu ³ (XENON Collaboration^¶)

¹Physics Department, Columbia University, New York, New York 10027, USA
²Nikhef and the University of Groningen, Van Swinderen Institute, 9747AG Groningen, Netherlands
³Kamioka Observatory, Institute for Cosmic Ray Research, and Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Higashi-Mozumi, Kamioka, Hida, Gifu 506-1205, Japan
⁴Physik-Institut, University of Zürich, 8057 Zürich, Switzerland
⁵LPNHE, Sorbonne Université, CNRS/IN2P3, 75005 Paris, France
⁶Institut für Kernphysik, University of Münster, 48149 Münster, Germany
⁷INFN-Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, 67100 L'Aquila, Italy
⁸Department of Physics, Enrico Fermi Institute & Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637, USA
⁹Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany
¹⁰New York University Abu Dhabi, Center for Astro, Particle and Planetary Physics, Abu Dhabi, United Arab Emirates
¹¹SUBATECH, IMT Atlantique, CNRS/IN2P3, Nantes Université, 44307 Nantes, France
¹²Department of Physics and Astronomy, University of Bologna and INFN-Bologna, 40126 Bologna, Italy
¹³Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001, Israel
¹⁴Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany
¹⁵Department of Physics & Center for High Energy Physics, Tsinghua University, Beijing 100084, People's Republic of China
¹⁶LIBPhys, Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal
¹⁷Nikhef and the University of Amsterdam, Science Park, 1098XG Amsterdam, Netherlands
¹⁸Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
¹⁹Institut für Physik & Exzellenzcluster PRISMA⁺, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
²⁰Department of Physics and Chemistry, University of L'Aquila, 67100 L'Aquila, Italy
²¹Institute for Astroparticle Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
²²INAF-Astrophysical Observatory of Torino, Department of Physics, University of Torino and INFN-Torino, 10125 Torino, Italy
²³Department of Physics “Ettore Pancini,” University of Napoli and INFN-Napoli, 80126 Napoli, Italy
²⁴Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
²⁵Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
²⁶Department of Physics, University of California San Diego, La Jolla, California 92093, USA
²⁷Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, and Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
²⁸Department of Physics, School of Science, Westlake University, Hangzhou 310030, People's Republic of China
²⁹Department of Physics, Kobe University, Kobe, Hyogo 657-8501, Japan
³⁰INFN-Ferrara and Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, 44122 Ferrara, Italy
³¹School of Science and Engineering, The Chinese University of Hong Kong (Shenzhen), Shenzhen, Guangdong, 518172, People's Republic of China

^*Also at INFN-Roma Tre, 00146 Roma, Italy.
^†Contact author: cfuselli@nikhef.nl
^‡Present address: Department of Physics & Astronomy, Bucknell University, Lewisburg, Pennsylvania, USA.
^§Contact author: ylin3@uni-muenster.de
^∥Also at Coimbra Polytechnic - ISEC, 3030-199 Coimbra, Portugal.
^¶Contact author: xenon@lngs.infn.it

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Phys. Rev. C 113, 044303 – Published 2 April, 2026

DOI: https://doi.org/10.1103/b3r7-6ff4

Abstract

We report the measurement of the ${}^{214}{Bi} β$ -decay spectrum to the ground state of ${}^{214}{Po}$ using the XENONnT detector. This decay is classified as first-forbidden nonunique, for which theoretical predictions require detailed nuclear structure modeling. A dedicated identification algorithm isolates a high-purity sample of ground-state $β$ decays, explicitly excluding events with associated $γ$ -ray emission. By comparing the measured spectrum, which covers energies up to $3.27 MeV$ , with several nuclear models, we find that the prediction based on the conserved vector current hypothesis provides the best description of the data. Using this dataset, we additionally derive charge and light yield curves for electronic recoils, extending detector response modeling up to the megaelectronvolt scale.

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References (54)

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Phys. Rev. C 113, 044303– Published 2 April, 2026

Vol. 113, Iss. 4 — April 2026

Received 9 October 2025
Accepted 25 February 2026

DOI: https://doi.org/10.1103/b3r7-6ff4

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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Spectral measurement of the ${}^{214}{Bi} β$ decay to the ${}^{214}{Po}$ ground state with the XENONnT Experiment

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Spectral measurement of the Bi214 β decay to the Po214 ground state with the XENONnT Experiment

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Physics Subject Headings (PhySH)

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References (54)

Spectral measurement of the ${}^{214}{Bi} β$ decay to the ${}^{214}{Po}$ ground state with the XENONnT Experiment