München 2019 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 23: Astroparticle Physics I

HK 23.2: Gruppenbericht

Dienstag, 19. März 2019, 14:30–15:00, HS 18

Status and prospects of the COBRA experiment — •Stefan Zatschler for the COBRA collaboration — TU Dresden, Institut für Kern- und Teilchenphysik

The COBRA experiment at the underground facility LNGS (Italy) is dedicated to the search for the hypothesized neutrinoless double beta-decay (0νββ-decay). The observation of this lepton number violating process would prove the Majorana nature of neutrinos and shed light on physics beyond the established Standard Model. In 2018 an upgrade of the COBRA demonstrator to the extended demonstrator (XDEM) was performed by adding nine 6 cm³ CdZnTe crystals to the existing 4×4×4 array of 1 cm³ detectors. COBRA XDEM uses improved prototypes of CdZnTe solid state detectors with an instrumented guard-ring electrode to veto surface events as the original demonstrator’s main background component. During the preparation phase of this upgrade the setup was optimized for low-threshold operation to investigate the fourfold forbidden non-unique β-decay of ¹¹³Cd. The spectral shape of the electron momentum distribution of this highly forbidden decay is expected to strongly dependent on an effective value of the weak axial-vector coupling strength g_A. For the scientific discussion regarding quenching effects that might affect the half-life predictions for the 0νββ-decay due to an effectively smaller value of g_A such experimental input is in high demand. This talk will present the current experimental status including first results of COBRA XDEM and summarize the spectral shape analysis of the ¹¹³Cd β-decay as well as ongoing studies of exotic ββ-decay modes. COBRA is funded by the DFG.