News

Congratulations to our summer student Tim Van de Vendel for receiving one of the three Best Presentation Awards at the CHIPP Summer Student Program 2026 (S3P3)!

Tim succesfully completed his two-month research project about the optical characterization of wavelength-shifting reflective materials in study to be employed in the liquid argon veto of the next-phase neutrinoless double beta decay experiment LEGEND-1000. Being the signal searched for very rare, efficient liquid argon scintillation light wavelength-shifter and reflective materials, together with a precise knowledge of their optical response, are of key importance. Tim contributed towards this important goal by operating the liquid argon setup, LArS, available at UZH, sensitive to different material light yields.

One of the other two awards was received by another UZH summer student, Zhoie Tan Lamanero, who studied quantum entanglement in Z → μ+ μ- at the CMS experiment in the group led by Ben Kilminster.
Congratulations to both Tim and Zhoie for their outstanding achievement!

The XENONnT experiment has recently achieved a new milestone in the study of solar neutrinos, observing neutrino–electron interactions at energies as low as 17keV with a significance of 5 sigma. The experiment's ultra-low background and low energy threshold allow it to detect these rare neutrino interactions, extending the accessible energy range by more than an order of magnitude compared to previous experiments (arXiv preprint). Solar neutrinos are produced by the nuclear fusion processes that power the Sun and provide a unique window into its core. This result demonstrates the potential of liquid-xenon detectors as multipurpose observatories, opening a new window into low-energy neutrino physics. Got curious? Please make sure to also have a look at the in-depth article on our UZH News page.

A potential site for a Swiss deep underground laboratory is currently being explored in the Bedretto Tunnel beneath the Gotthard massif in the canton of Ticino. Located 3.5 km from the tunnel entrance, the site lies beneath up to 1500 metres of rock. This natural shielding makes it an exceptional location for experiments that require an environment almost entirely free from interference caused by cosmic radiation.

The results of a comprehensive campaign to characterize the underground environment in the Bedretto tunnel have now beenpublished in European Physics Journal C. The study, which was carried out in close collaboration with the BedrettoLab group at the ETH Zürich, confirms the site's remarkable potential. In particular, the measured flux of cosmic muons is found to be reduced by a factor of one million inside the cavern. This would make the Bedretto Tunnel the second deepest underground laboratory site in Europe.

Transformer-based models outperform a feature-based baseline for pulse-shape discrimination in Majorana Demonstrator HPGe waveforms, with masked-autoencoder pre-training reducing the need for labelled data by factors of 2-4 in low-label regimes. Marta Babicz and collaborators published the study in Machine Learning: Science and Technology, showing how modern sequence-learning methods can use the full information contained in digitised detector waveforms.

Pulse-shape discrimination is a key tool in rare-event searches such as neutrinoless double-beta decay, where HPGe detectors must distinguish candidate signal-like events from backgrounds. Instead of compressing each waveform into a few hand-crafted summary quantities, the study trains detector-conditioned transformer models directly on charge traces and their gradients from the Majorana Demonstrator AI/ML data release. The transformers improve classification performance across standard PSD selections, especially for the more challenging labels and for the combined PSD-pass definition. The work also shows that self-supervised masked-autoencoder pre-training on unlabelled calibration data can make the models substantially more sample-efficient, an encouraging result for future applications in LEGEND-200, LEGEND-1000, and other HPGe-based low-background experiments.

You can read the paper in Machine Learning: Science and Technology, and the preprint is available as arXiv:2603.06192.

Congratulations to Dr. Andrea Paloma Cimental Chávez, who successfully defended her Ph.D. thesis this May!

During her thesis, Paloma worked on the XENONnT experiment at LNGS and on the Xenoscope facility at UZH. In particular, Paloma contributed to the background simulation development in the XENONnT high-energy regime (in the MeV region), and she investigated the sensitivity of the experiment to the 2vECß+ decay of Xe124. For Xenoscope, a vertical demonstrator for the future XLZD experiment, she succesfully designed and tested a new high-voltage delivery system bringing HV from air to vacuum to liquid xenon.

Congrats Paloma!!