Speaker
Description
We report the first observation of the positron emission process Xe-125 → e+ + ν + I-125 (Q=1.6 MeV) in a liquid xenon detector using post-calibration data from the LUX-ZEPLIN (LZ) experiment. We provide an independent measurement of the branching for this decay fraction with a statistical significance of 5.5σ. Xe-125 is a short-lived (τ1/2 ∼ 17 h) isotope of xenon which can be produced by neutron activation on natural xenon. 125Xe primarily decays by electron capture, but positron emission has been confirmed by direct measurement to at least the 243 keV level of I-125. An additional decay to the 188 keV level is suspected, but has not been directly confirmed. Existing measurements constrain only the total positron decay rate, determined via annihilation gamma-ray counting. This work presents the first determination of positron emission branching rate to the individual levels of I-125. LZ displays the ability of liquid xenon time projection chambers to search for more complex event topologies than the standard single scatter events expected from dark matter interactions.
| Main Contribution topic | Direct detection |
|---|---|
| Secondary contribution topic | Instrumentation for Dark Matter |