DrChristian Wittweg

My research aims to answer three fundamental questions of modern physics:

• What is the dark matter in the Universe?
• How is there matter in the Universe at all?
• What is the nature of neutrinos and their interactions?

In order to answer these questions, I look for exceedingly rare natural processes with sensitive low-background detectors. By directly measuring the scattering of dark matter particles off atomic nuclei within xenon dual-phase time projection chambers, we may soon decipher the mystery of dark matter. Using the same technology, we can measure extremely faint interactions of neutrinos – ghostly particles that will rarely interact with other matter. This allows us to learn about neutrino interactions themselves, but also about their sources such as the sun or dying stars. Lastly, xenon dual-phase time projection chambers can be used to look for extremely rare radioactive decays of the xenon atoms themselves. Hypothetically, these decay with half-lives many times longer than the age of the Universe via the so-called neutrinoless double-beta decay. If this decay were observed, it would indicate that neutrinos are their own anti-particles and that the matter-antimatter balance of the Universe is not conserved. This may give us an explanation why matter can exist after the Big Bang in the first place.

I am also exploring new ways of detecting neutrinos and neutrons with applications beyond fundamental science. The coherent elastic scattering of neutrinos off nuclei as well as common neutron interactions could be measured using the formation of fluorescent colour centre tracks in crystals. These tracks could then be measured using light-sheet fluorescence microscopy. The application of imaging and machine-learning based analysis methods from the medical and life sciences may allow to scan large crystal volumes quickly. Applications include the monitoring of nuclear facilities using neutrinos and neutron spectroscopy.

I have been a member of the following experiments or collaborations:

• XENON (2016–2025): analysis coordinator May 2022 – Jan 2024, photosensor group leader Jan 2024 – October 2025
• DARWIN (2016–2025): neutrinoless double beta decay
• XLZD (since 2022)
• PALEOCCENE (since 2025): imaging of colour centre tracks in crystals with mesoSPIM at UZH
• LUX-ZEPLIN (LZ, since 2026)
• Mineral Detection of Dark Matter (MDDM, since 2026)