Four million euros for state-of-the-art particle physics experiments and detector development
09.12.2025
Prof. Dr. Martin Fertl and Dr. Stefan Schoppmann from Johannes Gutenberg University Mainz (JGU) and the PRISMA+ Cluster of Excellence have each been awarded an ERC Consolidator Grant, one of the EU's most highly endowed grants, to support outstanding projects in experimental particle physics and detector development. Both projects aim to improve our understanding of fundamental physics.
The fundamental levels of nature are described by the Standard Model of particle physics. But despite its success, the model cannot explain some phenomena, such as the existence of dark matter or the excess of matter over antimatter. There are also several other mysteries, such as discrepancies between different measurements or discrepancies between experimental results and theoretical predictions. These mysteries show us that the Standard Model does not tell the whole story and provide initial clues to "new physics" beyond the Standard Model.
Precision measurements are a powerful approach to discovering physics beyond the Standard Model. To confirm that, for example, deviations between measurements do not have an experimental origin, the properties of nature must be observed with the highest precision. It is equally important to investigate rare processes experimentally. In these cases, the measurable effects are very small but extremely significant due to the information they provide. It is therefore necessary to be able to distinguish them from other processes and background events. This requires measurements and calculations that are extremely precise.
Thanks to the new funding, the two researchers will strengthen their teams in order to carry out two projects that will study subatomic particles: the neutron in the case of Fertl's 'NuLife' project, and the neutrino in the case of Schoppmann's 'NuDoubt++' project. These experiments aim to improve our understanding of the nature of particles and fundamental forces, and provide answers to open questions about the Standard Model and possible new physics.
Both projects are based on developments, studies, and work that have been ongoing for years. "In 2022, I joined JGU as part of the PRISMA Detector Innovation Postdoctoral Fellowship, which enabled me to acquire the necessary expertise and skills to plan and carry out an ambitious experiment such as NuDoubt++," explains Schoppmann, who is now a principal investigator at the PRISMA Detector Lab. In the case of NuLife, the preliminary work began even before the PRISMA+ Cluster of Excellence was established. "The development of a fully magnetic trap for neutrons, on which my project is based, was already initiated in the PRISMA Cluster of Excellence by my predecessor, Prof. Dr. Werner Heil," says Fertl. "In the PRISMA+ Cluster of Excellence, I then contributed my decisive ideas, on whose successful demonstration NuLife is now based."
NuDoubt++: a novel detector concept for measuring double beta decay
NuDoubt++ focuses on the study of an extremely rare nuclear process known as double beta plus decay, in which two positrons—particles that resemble electrons but have a positive charge—are released. This decay is difficult to detect due to its rarity, the complexity of the detection process, and the limited availability of suitable materials. However, the effort is worthwhile, as measurements of double beta decay are a powerful tool for investigating the nature of neutrinos. In particular, they can be used to test whether neutrinos are their own antiparticles, which would classify them as Majorana particles.
To this end, NuDoubt++ will push forward the use of scintillator materials. These are materials that emit light when charged particles or photons pass through them, making them ideal for their detection. The new class of bright slow hybrid scintillators developed at JGU can separate two types of light very well, making them suitable for positron detection. Typically, transparent crystals, plastics, or liquids are used for this purpose. However, NuDoubt++ will also use opaque scintillators. This involves a new type of material that will enable the experiment to significantly improve its sensitivity to double beta decay. "I developed the opaque scintillator technology in 2019 by mixing a classic transparent scintillator with wax," explains Schoppmann. "My current breakthrough in combining opaque and hybrid scintillators enables NuDoubt++ to benefit from all the advantages of scintillator detectors through a unified approach that maximizes measurement sensitivity. Over the past two years, I have led a research group at JGU that has developed a preliminary detector concept based on my idea using computer simulations. Now, we are ready to turn the concept into reality."
In the first year funded by the ERC Consolidator Grant, the concept and design of the detector will be finalized. In the second and third years, the detector will be built and tested in the experimental hall of the Institute of Physics at JGU. In the last two years of funding, NuDoubt++ will measure two-neutrino double beta plus decay and improve the precision of current experiments.
NuLife: a high-precision test of the structure of the weak interaction
The aim of the NuLife project is to determine the lifetime of neutrons as accurately as possible. This enables a high-precision test of the structure of the weak interaction, which determines countless phenomena, including the ratio of light elements in the early universe—such as helium to hydrogen—or the radioactive decay of neutrons and nuclei.
The NuLife project is being developed primarily in Mainz and will lay the groundwork for improving the precision of the future τSPECT2 experiment. τSPECT2 is based on the current τSPECT experiment, which is being conducted under the direction of Fertl's group at the Paul Scherrer Institute in Switzerland, and uses ultracold neutrons (UCN) to measure the lifetime of neutrons. Since these extremely slow neutrons can be stored, their lifetime can be determined by the number of neutrons that survive storage. NuLife is developing a groundbreaking superconducting trap for storing UCNs, which, combined with innovative beamline concepts, will dramatically increase the number of neutron decays observed. Modern UCN sources generate large numbers of very slow neutrons. "Successful implementation of NuLife will increase the number of neutrons stored in the τSPECT2 experiment by up to 200 compared to our prototype τSPECT setup," explains Fertl. "This will enable the τSPECT2 experiment to collect the large data sets required to determine the neutron lifetime with an accuracy of 0.1 seconds or better. This high level of precision will enable us to test whether the measured neutron lifetime aligns with the Standard Model of particle physics predictions and shed light on discrepancies between the most precise observations. Furthermore, highly sensitive investigations of the mathematical structure of the Standard Model will be possible, either setting very strict limits on physics beyond the Standard Model or discovering new weak interactions, new particles, and new structures of the weak interaction."
The NuLife project aims to fully translate the outstanding performance of the τSPECT experiment into unprecedented experimental precision in measuring the neutron lifetime, which could make it a reference point in research into physics beyond the Standard Model.