The 59th Winter Nuclear & Particle Physics Conference (WNPPC2022)

Status of the KDK Experiment: A Measurement of 40K Relevant for Rare-event Searches

18 Feb 2022, 13:24

12m

virtual

Nuclear and Particle Physics Particle Physics

Speaker

Lilianna Hariasz (Queen's University, Kingston, ON)

Description

Potassium-40 (${}^{40}$K) is a naturally-occurring, radioactive isotope of interest to rare-event searches as a challenging background. In particular, NaI scintillators contain ${}^{40}$K contamination which produces an irreducible $\sim 3\text{ keV}$ signal originating from this isotope's electron capture (EC) decays. In geochronology, the $\mathcal{O}(\text{Gy})$ lifetime of ${}^{40}$K is utilized in dating techniques. The direct-to-ground-state EC intensity ($I_{\text{EC}}$) of this radionuclide has never been measured, and theoretical predictions are highly variable ($I_{\text{EC}}\sim (0.05(1)–0.22(4))\mathrm{\%}$). The poorly understood intensity of this branch may affect the interpretation or precision of experimental results, including those probing DM signals in the (2-6) keV region. The KDK ("potassium decay") experiment is finalizing the first measurement of this $I_{\text{EC}}$ branch, which uses a coincidence technique between a high-resolution $\mathcal{O}(\text{keV})$ Silicon Drift Detector and a highly-efficient ($\sim 98\mathrm{\%}$) $\mathcal{O}(\text{MeV})$ Modular Total Absorption Spectrometer (Oak Ridge National Labs) to differentiate ground and excited state EC decays of ${}^{40}$K. We report on the status of the main ${}^{40}$K analysis leading up to unblinding, along with a preliminary measurement of Zinc-65 decays used to test analysis methods.

Presentation materials

status_of_the_KDK_experiment.pdf