Search for double $$\beta $$-decay modes of $$^{64}$$Zn using purified zinc

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2021-02, Vol.81 (2), Article 106
• Main Authors: Bellini, F., Beretta, M., Cardani, L., Carniti, P., Casali, N., Celi, E., Chiesa, D., Clemenza, M., Dafinei, I., Di Domizio, S., Ferroni, F., Gironi, L., Gorbenko, Yu. V., Gotti, C., Kovtun, G. P., Laubenstein, M., Nagorny, S., Nisi, S., Pagnanini, L., Pattavina, L., Pessina, G., Pirro, S., Previtali, E., Rusconi, C., Schäffner, K., Shcherban, A. P., Solopikhin, D. A., Virich, V. D., Tomei, C., Vignati, M.
• Format: Article
• Language: English
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-021-08918-y

The production of ultra-pure raw material is a crucial step to ensure the required background level in rare event searches. In this work, we establish an innovative technique developed to produce high-purity (99.999%) granular zinc. We demonstrate the effectiveness of the refining procedure by measuring the internal contaminations of the purified zinc with a high-purity germanium detector at the Laboratori Nazionali del Gran Sasso. The total activity of cosmogenic activated nuclides is measured at the level of a few mBq/kg, as well as limits on naturally occurring radionuclides are set to less than mBq/kg. The excellent radiopurity of the zinc sample allows us to search for electron capture with positron emission and neutrinoless double electron capture of $$^{64}$$ 64 Zn, setting the currently most stringent lower limits on their half-lives, $$T_{1/2}^{\varepsilon \beta ^+} > 2.7\times 10^{21}~\text {year}$$ T 1 / 2 ε β + > 2.7 × 10 21 year (90% CI), and $$T_{1/2}^{0\nu 2\varepsilon }> 2.6\times 10^{21}~\text {year}$$ T 1 / 2 0 ν 2 ε > 2.6 × 10 21 year (90% CI), respectively.