Speaker
Description
The nuclear matrix element for neutrinoless double beta decay of $^{76}$Ge can be expressed as a sum over all transitions along states of the intermediate nucleus $^{76}$As. The dominant contribution is expected to be the ground state of $^{76}$As. Experimentally the contribution of the $^{76}$As ground state can be investigated via the branching ratios of its $\beta^-$ and electron capture decay branches.
An $^{76}$As sample was produced by (n,$\gamma$) reactions on $^{75}$As using the AKR-2 reactor at TU Dresden. The branching ratio of $^{76}$As decaying to various $^{76}$Ge states by electron capture is measured in a low-background coincident counting setup consisting of a high-purity germanium detector and a silicon drift detector both mounted very close to the As sample. The experimental setup is located in the Felsenkeller shallow underground laboratory in Dresden reducing muon induced backgrounds. An additional passive shielding reduces the $\gamma$-induced background. Details of the experimental setup will be introduced.
