MEDEX'22

Spectrum-shape method for the 210Bi forbidden beta decay study using PbMoO4 cryogenic detectors.

Jun 15, 2022, 11:30 AM

30m

Conference room (Institute of Experimental and Applied Physics, CTU in Prague)

Oral presentation Experiment Experiment

Speaker

Dr Hyelim Kim (Institute for Basic Science)

Description

The spectrum-shape method has been proposed to determine the effective value of the axial-vector coupling constant, $g_A$ with the vector coupling constant, $g_v=1$ in forbidden nonunique $\beta$ decays. ${}^{210}$Bi nuclear is the isotope of first nonunique forbidden beta decay, the shape function of which strongly depends on the $g_A$.
Due to the short half-life of the ${}^{210}$Bi, the ${}^{210}$Pb ($\beta$, 22.3 y) $\to$ ${}^{210}$Bi ($\beta$, 5.0 d) $\to$ 210Po ($\alpha$, 138 d) decay chain has been adopted. PbMoO${}_4$ cryogenic detectors have been used for high detection efficiency (source = detector) and high energy resolution. We prepared 2 detectors of same detector geometric design and same crystal size (1 cm${}^3$). One PbMoO${}_4$ contains a modern lead and the ${}^{210}$Pb radioactivity was about 30 Bq/kg. The other PbMoO${}_4$ crystal contains an archeological lead with low radioactivity of ${}^{210}$Pb (about 0.2 Bq/kg) and has been used to reject the backgrounds with low systematic error. They were installed next to each other in a cryogen-free dilution refrigerator.
We will present the details of the detectors and properness of the pure beta decay spectrum collected by this detection system.

Presentation materials

202206_MEDEX2022_hlkim_pdf.pdf