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Volume 332 - XIV International Conference on Heavy Quarks and Leptons (HQL2018) - Neutrino Physics
Search for neutrinoless double beta decay with GERDA Phase II
K. von Sturm* on behalf of the GERDA Collaboration
*corresponding author
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Pre-published on: 2018 December 05
Published on: 2018 December 11
The GERDA Collaboration is searching for neutrinoless double beta (\zbb) decay of the candidate isotope $^{76}$Ge operating bare germanium detectors enriched in $^{76}$Ge to about $88\,\%$ in liquid argon (LAr). With the latest data release in May 2018 the best median sensitivity in the field of $T_{1/2}^{\beta\beta} > 1.1 \cdot 10^{26}\,$yr has been reached. This was possible due to the ultra-low background level of $BI = (5.6^{+3.4}_{-2.4})\cdot10^{-4}\,$cts/(kg$\,$keV$\,$yr) which has been achieved thanks to an active veto system detecting LAr scintillation light, an improved granularity of the detector array improving anti-coincidence background rejection, an extremely good energy resolution of O($0.1\,\%$) in the region of interest and an improved background rejection based on the distinct time profile with respect to signal events. A total exposure of $82.4\,$kg$\,$yr accumulated in two experimental phases were analyzed an no evidence for \zbb\ decay was found. The obtained frequentist half-life limit is $T_{1/2}^{\beta\beta} > 0.9 \cdot 10^{26}\,$yr at $90\,\%$C.L.
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