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Doctoral Dissertation at the Institute for Nuclear Physics on the MAGIX Experiment at the MESA Accelerator

We congratulate Dr. Sebastian Stengel on the successful completion of his dissertation entitled “Design and Development of the MAGIX Trigger Veto System”

In his dissertation, Sebastian Stengel developed, implemented, and tested a central detector system for the MAGIX experiment at the new electron accelerator MESA in Mainz.

The versatile MAGIX experiment is designed for high-precision investigations in nuclear and hadron physics, but also opens up other opportunities, including searches for so-called dark photons – hypothetical particles closely related to theories of dark matter. The detection of scattered particles is primarily achieved via two high-resolution magnetic spectrometers.

The focus of the work was the so-called trigger veto system of these spectrometers. It provides a fast and reliable trigger decision for data acquisition, records timing coincidences, and delivers crucial information for particle identification. In addition, it serves as a time reference for the readout of the spectrometer tracking detectors.

The system consists of a segmented trigger layer made of plastic scintillators read out by photomultipliers, as well as a flexible veto system composed of additional scintillator layers equipped with silicon photomultipliers and lead layers for background suppression. The readout is handled by a fast, high-rate FPGA-based electronics system.

Throughout the course of the work, all components of the system were designed, selected, tested, and systematically optimized – including the mechanical design for integration into the spectrometers. Both extensive simulations using Geant4 and comprehensive system tests under realistic experimental conditions were employed.

During a beam time at the MAMI accelerator, the trigger system achieved a remarkable detection efficiency of 99.93%, a time resolution of approximately 180 ps (FWHM), and a spatial resolution of about 25 mm – significantly surpassing the original design requirements. The system is now fully operational and ready for use in the upcoming MAGIX experiment.

The dissertation was carried out within the framework of the MAGIX Collaboration under the supervision of Prof. Achim Denig and impressively documents Sebastian Stengel’s contribution to the preparation of one of the key experiments at the MESA accelerator.

This work stands as an outstanding example of comprehensive, modern experimental detector development – from the conceptual phase to the successful implementation of a complex and high-performance detector system.

Johannes Gutenberg University Mainz receives further funding for participation in the Mu3e experiment

Scientists from the PRISMA+ Cluster of Excellence are involved in a major international research project searching for "new physics"

15 April 2025

photo/©: Niklaus Berger

The German Research Foundation (DFG) has extended its funding for the Mu3e experiment for another four years. The project, which is a collaboration of Johannes Gutenberg University Mainz (JGU), Heidelberg University, and the Karlsruhe Institute of Technology (KIT), will receive funding of EUR 5.6 million starting in May 2025. This extension of the DFG-funded Research Unit 5199 will enable the participating scientists to take further steps in the search for the violation of the lepton family number.

The Mu3e experiment, carried out at the Paul Scherrer Institute (PSI) in Villigen in Switzerland, is an international project which also involves researchers from Switzerland and the UK. The aim of the project is to observe a so-called lepton-flavor violating decay of a positive muon, in which the muon decays into two positrons and one electron. As this decay is not foreseen in the Standard Model of particle physics, the observation of this process would be a clear indication of new physics.

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Dissertation at the Institute of Nuclear Physics

We congratulate Dr. Viacheslav Tsaran on completing his dissertation entitled

Unified approach to nuclear pion scattering and photoproduction

A promising way to study how protons and neutrons are arranged inside atomic nuclei is by creating neutral pions through photon interactions with the nuclei. However, accurately modeling these interactions has been challenging. This research develops a new theoretical framework for pion production that accounts for the complex interactions between pions and nuclei.

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21-ton magnet installed in new MESA particle accelerator

Superconducting core component for international P2 experiment installed in underground hall at a depth of ten meters

25 November 2024

photo/©: Twain Wegner

One of the flagship projects of the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) is the construction of the new energy-recovering particle accelerator MESA (Mainz Energy-recovering Superconducting Accelerator), which will enable experiments with unprecedented precision in the future. One of the main experiments at MESA, P2, will play a key role in researching the "new physics" – physics beyond the Standard Model of particle physics – by measuring the so-called weak mixing angle. The central component of the P2 experiment, a superconducting magnet coil with a diameter of four meters and a weight of 21 tons, has now been delivered to the JGU campus and installed in the MESA particle accelerator. The magnet was manufactured in Vannes, France, and delivered to Mainz last Thursday. "We have been working together with the company SigmaPhi for almost five years to overcome the challenges and implement the state-of-the-art design for our experiment," said Professor Frank Maas, spokesperson of the P2 experiment, which is currently being set up by a collaboration of physicists from Germany, France, Canada, and the USA.

"Such a solenoid magnet is being used for experiments of this kind for the first time. Its large diameter makes it possible to record particularly high particle rates. However, the size of the magnet also posed a particular challenge in terms of design and production."

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Dissertation at the Intsitute of Nuclear Physics

We congratulate Marius Köppel on the completed dissertation entitled

"Data Flow in the Mu3e Data Acquisition System"

Marius Köppel has defended his PhD on the data acquisition system for the Mu3e experiment at PSI. Mu3e searches for the lepton-flavour-violating decay of a positive muon to two positrons and an electron. Marius has developed firmware for the data flow out of the detector to the filter farm and was instrumental to get the data acquisition and online analysis for the Mu3e integration and cosmic runs up and running. He has also contributed decisively to establishing the Mu3e MuPix pixel sensors as a tool for muon spin relaxation (MuSR) experiments. The thesis is available here.

Pierre Capel elected Fellow of the American Physical Society

Major award for theoretical physicist of Mainz University and member of the PRISMA+ Cluster of Excellence

8 October 2024

Pierre Capel, Professor of Theoretical Physics at the Institute for Nuclear Physics of Johannes Gutenberg University Mainz (JGU) and member of the PRISMA+ Cluster of Excellence, has been elected a Fellow of the American Physical Society (APS). This honor recognizes his careful and creative application of few-body methods to the study of nuclear reactions involving exotic nuclei. The APS Fellowship Program was established to recognize outstanding members who have made significant advances in physics through original research and publication. It is a distinct honor that signifies recognition by professional peers. Each year, no more than 0.5 percent of APS members are elected to the Fellow status.

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New CRC 1660: Hadrons and Nuclei as Discovery Tools

Collaborative Research Centre at JGU's Institute for Nuclear Physics seeks new physical phenomena through a better understanding of strong interaction processes

31 May 2024

The German Research Foundation (DFG) today approved the establishment of a new Collaborative Research Centre (CRC) at Johannes Gutenberg University Mainz (JGU). The CRC 1660 "Hadrons and Nuclei as Discovery Tools" aims to understand the strong interaction that leads to processes involving hadrons, nuclei, and atoms. The goal is to answer fundamental questions: What physical phenomena occur beyond the Standard Model of particle physics (SM) and how can we measure and describe them? The spokespersons of the new Collaborative Research Centre are Professor Concettina Sfienti (experiment) and Professor Marc Vanderhaeghen (theory) from the Institute for Nuclear Physics at JGU.

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Workshop "Strange hadrons as precision tool for strongly interacting systems (SPICE)"

24.05.24
From 13th to 17th may the workshop for Strange hadrons as precision tool for strongly interacting systems (SPICE) took place in Trento. “With 52 international participants and 39 keynote speakers, the conference offered a perfect platform to assess the present status of the field, to identify potential synergies within the community and to define experimental objectives for new cutting-edge research activities” Prof. Josef Pochodzalla, one of the organizers, resumes. To cover the field as broadly as possible a variety of topics were addressed during the five days workshop, including  hypernuclei, exotic atoms, femtoscopy, extreme neutron rich nuclei, the kaon-nucleus interaction and the strangeness in neutron stars.

The workshop was supported by the EU Strong 2020 project and ECT*.

DAAD prize for Francesca Bonaiti

Francesca Bonaiti is receiving the 2024 DAAD prize for international students

Francesca Bonaiti from the group of Sonia Bacca stands out as one of the top physics PhD students at JGU. Consistently achieving exceptional results in her theoretical research, she has published several papers in peer-reviewed journals. Recognized for her strong potential, she also has collected several invitations to international conferences and has recently secured the prestigious 5-year FRIB theory fellow position in the USA.

Francesca Bonaiti's research lies in the field of theoretical nuclear physics. Employing complex computational tools, she studies the behaviour of atomic nuclei immersed in electric and magnetic fields, starting from the strong force binding protons and neutrons together in the nucleus. Her work, deepening our knowledge of nuclear structure, helps in advancing our understanding of the nature of neutron stars.

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ERC Advanced Grant for Maarten Boonekamp in collaboration with Jens Erler und Frank Maas

New physics in parity violation: From the Thomson limit to the energy frontier / Funding worth EUR 3.2 million

11 April 2024

Professor Maarten Boonekamp, Professor Frank Maas, Professor Jens Erler (photo/©: private / Sabrina Hopp)

The consortium of Professor Maarten Boonekamp from Université Paris-Saclay as spokesperson and Professor Jens Erler and Professor Frank Maas of Johannes Gutenberg University Mainz has been awarded an ERC Advanced Grant for their project Zeptometry. This project aims to combine new precision measurements at the highest LHC energies at the European Organization for Nuclear Research CERN with challenging new precision measurements at very low energies with the upcoming MESA accelerator in Mainz in connection with the theory interpretation of the experimental results. The funding will be dedicated to the study of interactions between the Z boson and the fermions, i.e., the quarks and leptons constituting ordinary matter, to which end the upcoming experiment P2 at the Mainz electron accelerator MESA will be crucial.

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