Speaker
Description
Currently-running and planned neutrinoless double beta decay ($0\nu$-DBD) experiments aim to reach an experimental sensitivity in terms of half-life at the order of 10$^{27}$–10$^{28}$ yr to probe the inverted neutrino hierarchy using a short list of isotopes – $^{76}$Ge, $^{100}$Mo, $^{130}$Te and $^{136}$Xe. However, $^{96}$Zr is also a promising nuclide due to its high energy transition (Q$_{2\beta}$ = 3.35 MeV) that helps to overcome the issue with the environmental gamma-radioactivity (up to 2.6 MeV) and internal beta-active nuclides from U/Th decay chains (up to 3.27 MeV). The high transition energy is also favorable from a theoretical point of view, as the expected half-life for $0\nu$-DBD is proportional to (Q$_{2\beta}$)$^{5}$.
Here we present the first complex study of Cs$_2$ZrCl$_6$ (CZC) scintillating crystals in terms of their chemical- and radio-purity, scintillating performance and pulse-shape discrimination ability. The low-background measurements with two CZC crystals (11 g and 24 g) over 456.5 days, supported their high radiopurity leading to a counting rate of 0.17 (kg$\cdot$keV$\cdot$yr)$^{-1}$ at the Q$_{2\beta}$ of $^{96}$Zr. Limits on different DBD modes of $^{96}$Zr were set at the level T$_{1/2}$ $\sim$ 10$^{17}$-10$^{20}$ yr (90$\%$ C.L.). The detailed analysis of the internal background components was performed to be used in further developments of Cs$_2$ZrCl$_6$ detectors and to optimize the future experiment.
| Submitted on behalf of a Collaboration? | No |
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