TY - JOUR

T1 - Characterization of the ionization response of argon to nuclear recoils at the keV scale with the ReD experiment

AU - Agnes, P.

AU - Ahmad, I.

AU - Albergo, S.

AU - Albuquerque, I.

AU - Corona, M. Atzori

AU - Ave, M.

AU - Bottino, B.

AU - Cadeddu, M.

AU - Caminata, A.

AU - Canci, N.

AU - Caravati, M.

AU - Consiglio, L.

AU - Davini, S.

AU - Dias, L. K.S.

AU - Dolganov, G.

AU - Fiorillo, G.

AU - Franco, D.

AU - Gulino, M.

AU - Hessel, T.

AU - Kemmerich, N.

AU - Kimura, M.

AU - Kuźniak, M.

AU - La Commara, M.

AU - Machts, J.

AU - Matteucci, G.

AU - Santos, E. Moura

AU - Nikoloudaki, E.

AU - Oleynikov, V.

AU - Pandola, L.

AU - Varona, R. Perez

AU - Pino, N.

AU - Puglia, S. M.R.

AU - Rescigno, M.

AU - Costa, B. Sales

AU - Sanfilippo, S.

AU - Sung, A.

AU - Sunny, C.

AU - Suvorov, Y.

AU - Tartaglia, R.

AU - Testera, G.

AU - Tricomi, A.

AU - Wada, M.

AU - Wang, Y.

AU - Wojaczyński, R.

AU - Zakhary, P.

N1 - Characterization of the ionization response of argon to nuclear recoils at the keV scale with the ReD experiment / P. Agnes, I. Ahmad, S. Albergo [et al.] // The European Physical Journal C - Particles and Fields. – 2026. – Vol. 86, No. 3. – P. 220. – DOI 10.1140/epjc/s10052-026-15410-y. – EDN MVQOWS. This work has been supported by the PRIN2022 grant 2022JCYC9E, call for tender No. 104 published on 2.2.2022 of the Italian Ministry of University and Research (MUR) under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, funded by the European Union – NextGenerationEU, CUP I53D23000690006. This work is supported by the NCN, Poland (2021/42/E/ST2/00331), the EU’s Horizon 2020 (No 952480, DarkWave project), IRAP AstroCeNT (Grant No. MAB/2018/7) funded by FNP from ERDF, and the São Paulo Research Foundation (FAPESP) (Grant No. 2021/11489-7). The authors also acknowledge the support of the French Agence Nationale de la Recherche (ANR), under grants ANR-22- CE31-0021 (project X-ArT) and ANR-23-CE31-0015 (project FIDAR), and of IN2P3–COPIN (No. 20-152). This work is also supported by the National Key Research and Development Project of China, Grant No. 2022YFA1602001. For the purpose of open access, the authors have applied a Creative Commons Attribution (CC BY) public copyright license to any Author Accepted Manuscript version arising from this submission.

PY - 2026/3/5

Y1 - 2026/3/5

N2 - In the recent years, argon-based experiments looking for Dark Matter in the Universe have explored the non-standard scenario in which Dark Matter is made by low-mass Weakly Interacting Massive Particles, of mass in the range of 1–10 GeV instead of the canonical hundreds of GeV. Detecting such particles is challenging, as their expected signatures are nuclear recoils with energies below 10 keV, observable solely via ionization. This necessitates a precise understanding of the detector response in this energy regime, which remains incomplete for argon. To address this, the ReD experiment was developed within the framework of the DarkSide-20k Collaboration to produce and characterize few-keV nuclear recoils. A compact dual-phase argon Time Projection Chamber (TPC) was irradiated with neutrons from a 252Cf source, to produce Ar recoils in the energy range of interest via (n,n’) elastic scattering. A downstream spectrometer composed of 18 plastic scintillators detected the neutrons scattered off Ar nuclei, enabling recoil energy reconstruction via two-body kinematics. The ionization yield Qy of argon, defined as the number of electrons produced per unit energy deposit, was measured in a model-independent way between 2 and 10 keV. These measurements extend direct experimental coverage well below the previous limit of approximately 7 keV. The results are consistent with existing data above 7 keV, while they indicate a higher Qy at lower energies.

AB - In the recent years, argon-based experiments looking for Dark Matter in the Universe have explored the non-standard scenario in which Dark Matter is made by low-mass Weakly Interacting Massive Particles, of mass in the range of 1–10 GeV instead of the canonical hundreds of GeV. Detecting such particles is challenging, as their expected signatures are nuclear recoils with energies below 10 keV, observable solely via ionization. This necessitates a precise understanding of the detector response in this energy regime, which remains incomplete for argon. To address this, the ReD experiment was developed within the framework of the DarkSide-20k Collaboration to produce and characterize few-keV nuclear recoils. A compact dual-phase argon Time Projection Chamber (TPC) was irradiated with neutrons from a 252Cf source, to produce Ar recoils in the energy range of interest via (n,n’) elastic scattering. A downstream spectrometer composed of 18 plastic scintillators detected the neutrons scattered off Ar nuclei, enabling recoil energy reconstruction via two-body kinematics. The ionization yield Qy of argon, defined as the number of electrons produced per unit energy deposit, was measured in a model-independent way between 2 and 10 keV. These measurements extend direct experimental coverage well below the previous limit of approximately 7 keV. The results are consistent with existing data above 7 keV, while they indicate a higher Qy at lower energies.

KW - Atomic Cluster Collisions

KW - Atomic Spectroscopy

KW - Experimental Nuclear Physics

KW - Nuclear Chemistry

KW - Nuclear astrophysics

KW - Nuclear Physics

UR - https://www.scopus.com/pages/publications/105033812857

UR - https://www.elibrary.ru/item.asp?id=90016069

UR - https://www.mendeley.com/catalogue/9f7567fd-ff70-3f4e-9e5b-40bb3a497290/

U2 - 10.1140/epjc/s10052-026-15410-y

DO - 10.1140/epjc/s10052-026-15410-y

M3 - Article

VL - 86

JO - European Physical Journal C

JF - European Physical Journal C

SN - 1434-6044

IS - 3

M1 - 220

ER -