Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 65: Niederenergie-Neutrinophysik 3

T 65.3: Talk

Tuesday, March 25, 2014, 17:20–17:35, P106

Study of the double beta decay of ⁷⁶Ge into excited states of ⁷⁶Se — •Thomas Wester for the GERDA collaboration — Institut für Kern und Teilchenphysik, TU Dresden

The Germanium Detector Array Gerda is an experiment searching for the neutrinoless double beta decay in ⁷⁶Ge. The observation of such a decay would prove the Majorana character of the neutrino and could provide a hint about the neutrino mass and possibly identify the mass hierarchy scheme.
The half life of the neutrino accompanied double beta decay (2νββ) of ⁷⁶Ge has been measured by Gerda Phase I with unprecedented precision. The observed spectrum comes mostly from from the transition from the 0⁺ ground state of ⁷⁶Ge to the 0⁺ ground state of ⁷⁶Se. However, phase space suppressed 2νββ transitions to excited states of ⁷⁶Se exist as well. At current state, the predicted half lives for such decays vary by several orders of magnitute, due to the large uncertainties in the nuclear matrix elements and the available nuclear models. An observation would therefore help to constrain model parameters and decrease those uncertainties.
A first search for this decay mode using the data from Phase I is currently in progress, which is based on a counting method. Several signal cuts have been investigated and optimized for a maximum in sensitiviy with the help of Monte Carlo simulations to estimate efficiencies and background contributions.
The presentation will discuss the current status and first results of this analysis.