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arXiv · 2508.19117

Flow-dependent tagging of $^{214}$Pb decays in the LZ dark matter detector

J. Aalbers·D. S. Akerib·A. K. Al Musalhi·F. Alder·C. S. Amarasinghe·A. Ames·T. J. Anderson·N. Angelides·H. M. Araújo·J. E. Armstrong·M. Arthurs·A. Baker·S. Balashov·J. Bang·J. W. Bargemann·E. E. Barillier·K. Beattie·T. Benson·A. Bhatti·T. P. Biesiadzinski·H. J. Birch·E. Bishop·G. M. Blockinger·B. Boxer·C. A. J. Brew·P. Brás·S. Burdin·M. C. Carmona-Benitez·M. Carter·A. Chawla·H. Chen·Y. T. Chin·N. I. Chott·M. V. Converse·R. Coronel·A. Cottle·G. Cox·D. Curran·C. E. Dahl·I. Darlington·S. Dave·A. David·J. Delgaudio·S. Dey·L. de Viveiros·L. Di Felice·C. Ding·J. E. Y. Dobson·E. Druszkiewicz·S. Dubey·C. L. Dunbar·S. R. Eriksen·A. Fan·N. M. Fearon·N. Fieldhouse·S. Fiorucci·H. Flaecher·E. D. Fraser·T. M. A. Fruth·R. J. Gaitskell·A. Geffre·J. Genovesi·C. Ghag·A. Ghosh·R. Gibbons·S. Gokhale·J. Green·M. G. D. van der Grinten·J. J. Haiston·C. R. Hall·T. Hall·S. Han·E. Hartigan-O'Connor·S. J. Haselschwardt·M. A. Hernandez·S. A. Hertel·G. J. Homenides·M. Horn·D. Q. Huang·D. Hunt·E. Jacquet·R. S. James·M. K. K·A. C. Kaboth·A. C. Kamaha·D. Khaitan·A. Khazov·J. Kim·Y. D. Kim·J. Kingston·R. Kirk·D. Kodroff·E. V. Korolkova·H. Kraus·S. Kravitz·L. Kreczko·V. A. Kudryavtsev·C. Lawes·D. S. Leonard·K. T. Lesko
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Abstract

The LUX-ZEPLIN (LZ) experiment is searching for dark matter interactions in a liquid xenon time projection chamber (LXe-TPC). This article demonstrates how control of the flow state in the LXe-TPC enables the identification of pairs of sequential alpha-decays, which are used to map fluid flow and ion drift in the liquid target. The resulting transport model is used to tag \UChPb~ beta-decays, a leading background to dark matter signals in LZ. Temporally evolving volume selections, at a cost of 9.0\% of exposure, target the decay of each \UChPb~ atom up to 81 minutes after production, resulting in (63~$\pm$~6$_{(\mathrm{stat})}$~$\pm$~7$_{(\mathrm{sys})}$)\% identification of \UChPb~decays to ground state. We also demonstrate how flow-based tagging techniques enable a novel calibration side band that is concurrent with science data. Finally we report updated estimates of radon-chain charge branching fractions in liquid xenon, finding branching to $^{218}$Po$^+$ at $0.49 \pm 0.01$, $^{214}$Pb$^+$ at $0.48 \pm 0.12$, and $^{214}$Bi$^+$ at $0.74 \pm 0.05$, with a mean charged ion lifetime in the LZ TPC of $49 \pm 4$ min.

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J. Aalbers, D. S. Akerib, A. K. Al Musalhi, F. Alder, C. S. Amarasinghe, A. Ames, T. J. Anderson, N. Angelides, H. M. Araújo, J. E. Armstrong, M. Arthurs, A. Baker, S. Balashov, J. Bang, J. W. Bargemann, E. E. Barillier, K. Beattie, T. Benson, A. Bhatti, T. P. Biesiadzinski, H. J. Birch, E. Bishop, G. M. Blockinger, B. Boxer, C. A. J. Brew, P. Brás, S. Burdin, M. C. Carmona-Benitez, M. Carter, A. Chawla, H. Chen, Y. T. Chin, N. I. Chott, M. V. Converse, R. Coronel, A. Cottle, G. Cox, D. Curran, C. E. Dahl, I. Darlington, S. Dave, A. David, J. Delgaudio, S. Dey, L. de Viveiros, L. Di Felice, C. Ding, J. E. Y. Dobson, E. Druszkiewicz, S. Dubey, C. L. Dunbar, S. R. Eriksen, A. Fan, N. M. Fearon, N. Fieldhouse, S. Fiorucci, H. Flaecher, E. D. Fraser, T. M. A. Fruth, R. J. Gaitskell, A. Geffre, J. Genovesi, C. Ghag, A. Ghosh, R. Gibbons, S. Gokhale, J. Green, M. G. D. van der Grinten, J. J. Haiston, C. R. Hall, T. Hall, S. Han, E. Hartigan-O'Connor, S. J. Haselschwardt, M. A. Hernandez, S. A. Hertel, G. J. Homenides, M. Horn, D. Q. Huang, D. Hunt, E. Jacquet, R. S. James, M. K. K, A. C. Kaboth, A. C. Kamaha, D. Khaitan, A. Khazov, J. Kim, Y. D. Kim, J. Kingston, R. Kirk, D. Kodroff, E. V. Korolkova, H. Kraus, S. Kravitz, L. Kreczko, V. A. Kudryavtsev, C. Lawes, D. S. Leonard, K. T. Lesko. 2025-08-26. Flow-dependent tagging of $^{214}$Pb decays in the LZ dark matter detector. https://arxiv.org/abs/2508.19117

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