Background determination for the LUX-ZEPLIN dark matter experiment
J. Aalbers, D. S. Akerib, A. K. Al Musalhi, F. Alder, S. K. Alsum, C. S. Amarasinghe, A. Ames, Tyler Anderson, N. Angelides, H. M. Araújo, J E Armstrong, M. Arthurs, Alexander A. Baker, J. Bang, J. W. Bargemann, A. Baxter, K. Beattie, P. Beltrame, E. P. Bernard, A. Bhatti, A. Biekert, T. P. Biesiadzinski, H. J. Birch, G. M. Blockinger, B. Boxer, C. A. J. Brew, P. Brás, S. Burdin, M. Buuck, R. Cabrita, M. C. Carmona-Benitez, C. Chan, A. Chawla, H. Chen, A. P. S. Chiang, N. Chott, M. V. Converse, A. Cottle, G. A. Cox, Oisín Creaner, C. E. Dahl, A. David, Sourav Dey, L. de Viveiros, C. Ding, J. E. Y. Dobson, E. Druszkiewicz, S. R. Eriksen, A. Fan, N. M. Fearon, S. Fiorucci, H. Flaecher, E. D. Fraser, T. Fruth, R. J. Gaitskell, J. Genovesi, C. Ghag, R. Gibbons, M. G. D. Gilchriese, S. Gokhale, J. Green, M. G. D. van der Grinten, C. B. Gwilliam, C. Hall, S. Han, E. Hartigan-O’Connor, S. J. Haselschwardt, S. A. Hertel, G. Heuermann, M. Horn, D. Q. Huang, D. Hunt, C. M. Ignarra, R. G. Jacobsen, O. Jahangir, R. S. James, J. Johnson, A. C. Kaboth, A. C. Kamaha, D. Khaitan, I. Khurana, R. Kirk, D. Kodroff, L. Korley, E. V. Korolkova, H. Kraus, S. Kravitz, L. Kreczko, B. Krikler, V. A. Kudryavtsev, E. Leason, J. Lee, D. S. Leonard, K. T. Lesko, C. Levy, J. Lin, A. Lindote, R. Linehan, W. H. Lippincott, X. Liu
Abstract
The LUX-ZEPLIN experiment recently reported limits on WIMP-nucleus interactions from its initial science run, down to $9.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}48}\text{ }\text{ }{\mathrm{cm}}^{2}$ for the spin-independent interaction of a $36\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$ WIMP at 90% confidence level. In this paper, we present a comprehensive analysis of the backgrounds important for this result and for other upcoming physics analyses, including neutrinoless double-beta decay searches and effective field theory interpretations of LUX-ZEPLIN data. We confirm that the in-situ determinations of bulk and fixed radioactive backgrounds are consistent with expectations from the ex-situ assays. The observed background rate after WIMP search criteria were applied was $(6.3\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{events}/{\mathrm{keV}}_{ee}/\mathrm{kg}/\mathrm{day}$ in the low-energy region, approximately 60 times lower than the equivalent rate reported by the LUX experiment.