The pre-dominance of ordinary matter over anti-matter in the observable universe is one of the greatest unsolved mysteries of cosmology. Without this asymmetry the universe would likely be a void. A possible explanation is the process of neutrinoless double beta decay, which could prove that matter and anti-matter are identical in certain situations.

The NuDoubt⁺⁺ experiment aims to measure two-neutrino and neutrinoless positive double weak decays (2β⁺/ECβ⁺). It is based on a new detector concept combining hybrid and opaque scintillators paired with a novel light read-out technique. The technology is particularly suitable for detecting positron (β⁺) signatures. In its first phase, NuDoubt⁺⁺ is going to operate under high-pressure loading of enriched Krypton-78 gas. It expects to measure for the very first time two-neutrino positive double weak decay modes within 1 tonne-week exposure. Moreover, NuDoubt⁺⁺ is expected to probe neutrinoless positive double weak decay modes at several orders of magnitude higher significance than current experimental limits.

The parasitic electron beam-dump experiment DarkMESA at the MESA accelerator in Mainz has a powerful discovery potential for dark sector particles in the light mass range. If light dark matter couples to electrons via vector mediators called dark photons, it would be produced copiously in the relativistic electron-nucleus collisions taking place in the dump. Simulation studies show that DarkMESA is complementary to experiments at proton beam facilities. The studies indicate that DarkMESA has the potential to be sensitive to the light dark matter thermal relic targets, that are predicted by the annihilation cross sections for reproducing today’s dark matter density.

In many neutrino experiments, the use of liquid scintillator as a detector material plays a decisive role. The loading of scintillator with metals allows a wide variety of usage cases. Special mixtures of different liquid scintillators allow precise adjustment of scintillator properties. However, despite their versatility, liquid scintillators also show disadvantages. A high load of non-scintillating additives, e.g. metal compounds, quickly leads to a low light yield, which makes the scintillator unusable. Likewise, even with unloaded scintillators, the absorption length limits the maximum size of detectors and the scintillation process itself leads to poor spatial and directional resolution.

Two novel approaches allow to overcome these flaws: On the one hand, one can use a hybrid approach like the combination of water and scintillator or a slow scintillator to produce a detector material which has the high light yield of scintillators and the good directional resolution of water-Cherenkov detectors. On the other hand, one can render the scintillator opaque and instrument it with localised light read-out which allows better vertex resolution and, at the same time, higher loading.

We research properties and production techniques for both types of media and their combination. Here we develop liquid and plastic scintillators involving novel manufacturing techniques such as additive printing. In this research, we work together closely with the PRISMA Detector Laboratory and international cooperation partners.