https://doi.org/10.1140/epjc/s10052-025-14105-0
Regular Article - Experimental Physics
The neutron veto of the XENONnT experiment: results with demineralized water
1
Physics Department, Columbia University, 10027, New York, NY, USA
2
Nikhef and the University of Groningen, Van Swinderen Institute, 9747AG, Groningen, Netherlands
3
Kamioka Observatory, Institute for Cosmic Ray Research, and Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Higashi-Mozumi, Kamioka, 506-1205, Hida, Gifu, Japan
4
LPNHE, Sorbonne Université, CNRS/IN2P3, 75005, Paris, France
5
Institut für Kernphysik, University of Münster, 48149, Münster, Germany
6
Department of Physics, INAF-Astrophysical Observatory of Torino, University of Torino and INFN-Torino, 10125, Turin, Italy
7
INFN-Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, 67100, L’Aquila, Italy
8
Department of Physics, Enrico Fermi Institute, Kavli Institute for Cosmological Physics, University of Chicago, 60637, Chicago, IL, USA
9
New York University Abu Dhabi-Center for Astro, Particle and Planetary Physics, Abu Dhabi, United Arab Emirates
10
Physik-Institut, University of Zürich, 8057, Zurich, Switzerland
11
SUBATECH, IMT Atlantique, CNRS/IN2P3, Nantes Université, 44307, Nantes, France
12
Department of Physics and Astronomy, University of Bologna and INFN-Bologna, 40126, Bologna, Italy
13
Max-Planck-Institut für Kernphysik, 69117, Heidelberg, Germany
14
Physikalisches Institut, Universität Freiburg, 79104, Freiburg, Germany
15
Department of Particle Physics and Astrophysics, Weizmann Institute of Science, 7610001, Rehovot, Israel
16
Department of Physics, Center for High Energy Physics, Tsinghua University, 100084, Beijing, People’s Republic of China
17
Department of Physics, LIBPhys, University of Coimbra, 3004-516, Coimbra, Portugal
18
Nikhef and the University of Amsterdam, Science Park, 1098 XG, Amsterdam, Netherlands
19
Department of Physics, Oskar Klein Centre, Stockholm University, AlbaNova, 10691, Stockholm, Sweden
20
Institut für Physik & Exzellenzcluster PRISMA+, Johannes Gutenberg-Universität Mainz, 55099, Mainz, Germany
21
Department of Physics and Chemistry, University of L’Aquila, 67100, L’Aquila, Italy
22
Institute for Astroparticle Physics, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
23
Department of Physics and Astronomy, Purdue University, 47907, West Lafayette, IN, USA
24
Department of Physics “Ettore Pancini”, University of Napoli and INFN-Napoli, 80126, Naples, Italy
25
Department of Physics and Astronomy, Rice University, 77005, Houston, TX, USA
26
Department of Physics, University of California San Diego, 92093, La Jolla, CA, USA
27
Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, and Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, 464-8602, Nagoya, Aichi, Japan
28
Department of Physics, School of Science, Westlake University, 310030, Hangzhou, People’s Republic of China
29
Department of Physics, Kobe University, 657-8501, Kobe, Hyogo, Japan
30
INFN-Ferrara and Dip. di Fisica e Scienze della Terra, Universitá di Ferrara, 44122, Ferrara, Italy
31
School of Science and Engineering, The Chinese University of Hong Kong, 518172, Shenzhen, Guangdong, People’s Republic of China
32
INFN-Roma Tre, 00146, Rome, Italy
33
Department of Physics and Astronomy, Bucknell University, Lewisburg, PA, USA
34
Coimbra Polytechnic-ISEC, 3030-199, Coimbra, Portugal
35
Institut für Kernphysik, University of Münster, 48149, Münster, Germany
Received:
13
December
2024
Accepted:
21
March
2025
Published online:
24
June
2025
Radiogenic neutrons emitted by detector materials are one of the most challenging backgrounds for the direct search of dark matter in the form of weakly interacting massive particles (WIMPs). To mitigate this background, the XENONnT experiment is equipped with a novel gadolinium-doped water Cherenkov detector, which encloses the xenon dual-phase time projection chamber (TPC). The neutron veto (NV) can tag neutrons via their capture on gadolinium or hydrogen, which release 
-rays that are subsequently detected as Cherenkov light. In this work, we present the first results of the XENONnT NV when operated with demineralized water only, before the insertion of gadolinium. Its efficiency for detecting neutrons is 
, the highest neutron detection efficiency achieved in a water Cherenkov detector. This enables a high efficiency of 
for the tagging of WIMP-like neutron signals, inside a tagging time window of 
between TPC and NV, leading to a livetime loss of 
during the first science run of XENONnT.
© The Author(s) 2025
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Funded by SCOAP3.
