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The broad physics reach of the LUX-ZEPLIN (LZ) experiment covers rare phenomena beyond the direct detection of dark matter. We report precise measurements of the extremely rare decay of ^124Xe through the process of two-neutrino double electron capture (22EC), utilizing a 1. 39\, kg yr isotopic exposure from the first LZ science run. A half-life of T₁/₂^22EC = (1. 09 0. 14ₒₓ₀ₓ 0. 05ₒₘₒ) 10^22\, yr is observed with a statistical significance of 8. 3\, , in agreement with literature. First empirical measurements of the KK capture fraction relative to other K-shell modes were conducted, and demonstrate consistency with respect to recent signal models at the 1. 4\, level.
Aalbers et al. (2024) studied this question.