München 2019 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 23: Astroparticle Physics I

HK 23.3: Talk

Tuesday, March 19, 2019, 15:00–15:15, HS 18

Double beta decay transitions of ⁷⁶Ge into excited states of ⁷⁶Se — •Thomas Wester and Birgit Schneider for the GERDA collaboration — IKTP, TU Dresden

The search for the neutrinoless double beta decay is one of the most active fields in modern neutrino physics. An observation would imply lepton number violation and provide valuable information about the neutrino mass mechanism. The GERDA experiment searches for the neutrinoless double decay in ⁷⁶Ge, by operating an array of isotopically enriched germanium detectors in a liquid argon cryostat.

This contribution discusses the search for two-neutrino and neutrinoless double beta decay transitions of ⁷⁶Ge into the three energetically lowest excited states of ⁷⁶Se performed with the Phase II data of GERDA. Due to phase space suppression, the predicted half-lives of those transitions are longer than the ground state transitions. Unfortunately, the predictions additionally vary by several orders of magnitude, due to large uncertainties in the calculations of the nuclear matrix elements. An observation of even the two-neutrino modes would therefore help to constrain model parameters and decrease such uncertainties also for neutrinoless transitions into the ground state and excited states. The sensitivity of GERDA covers several of the predicted half-lives.

An event counting method is performed based on coincident events between two germanium detectors. The analysis procedure and preliminary results will be presented.