“Research with neutrons is great fun”: MLZ Prize for Stephan Paul

From day one, Prof. Dr. Stephan Paul, as he says, “took the research reactor to his heart,” sat on the MLZ supervisory board, and helped develop the scientific instruments. Now, the professor of hadron and particle physics with neutrons at the Technical University of Munich (TUM) has been awarded the MLZ Prize for Instrumentation and Scientific Use for his many years of commitment.

Prof. Dr. Stephan Paul The two MLZ directors, Prof. Dr. Martin Müller (right) and Prof. Dr. Christian Pfleiderer (left), presented the MLZ Prize 2025 to Prof. Dr. Stephan Paul. © Iris Köhler, Forschungszentrum Jülich / MLZ

The two MLZ directors, Prof. Dr. Martin Müller (right) and Prof. Dr. Christian Pfleiderer (left), presented the MLZ Prize 2025 to Prof. Dr. Stephan Paul. © Iris Köhler, Forschungszentrum Jülich / MLZ

The award was presented to him by Prof. Christian Pfleiderer and Prof. Martin Müller, the scientific directors of the MLZ, during the MLZ User Meeting at the end of 2025. Laudator Christian Pfleiderer recounts his early years at the Technical University of Munich, where, as a newly appointed professor, he received valuable advice from Stephan Paul and jointly conducted final examinations. “I was somewhat relieved that I did not have to answer these questions myself,” Christian Pfleiderer admits.

“Shaped the entire community”

Stephan Paul joined the FRM II and the MLZ very early on. From 2008 to 2010, he was a member of the Instrumentation Council, and from 2011 to 2020, he was a member of the MLZ Coordination Council “from day one,” as laudator Christian Pfleiderer says. “Stephan Paul is someone who has shaped an entire community. He is the representative for particle physics with neutrons,” says Christian Pfleiderer, praising his colleague.

Getting instruments up and running

In his subsequent plenary lecture, Stephan Paul expresses his gratitude for the “tremendous honor” of receiving the award. “I took the research reactor to my heart from day one and was actively involved in getting the instruments at FRM II up and running,” he adds.

How did antimatter disappear?

Then he moves straight on to his topic: neutrons in particle physics and ultra-cold neutrons in particular: “It’s great fun doing research with neutrons,” says Stephan Paul, revealing his passion right at the start. You can “run up to” ultra-cold neutrons because they only travel at a speed of 5 meters per second. And according to Stephan Paul, these neutrons are extremely important for understanding how the universe evolved after the Big Bang. Were there more than three spatial dimensions? Why is there less antimatter than matter?

Presentation_Prof. Dr. Stephan Paul In his plenary lecture at the MLZ User Meeting, Stephan Paul explained how neutrons can be used to investigate the origin of the universe. © Iris Köhler, Forschungszentrum Jülich / MLZ

In his plenary lecture at the MLZ User Meeting, Stephan Paul explained how neutrons can be used to investigate the origin of the universe. © Iris Köhler, Forschungszentrum Jülich / MLZ

Ultracold neutron source

All of this can be investigated with the scientific neutron instruments developed and maintained by Stephan Paul’s chair: the planned ultracold neutron source, which will supply two instruments.

When presenting the award, a miniature model of the FRM II reactor, Stephan Paul elicits laughter from the approximately 250 scientific guests: “Wow, where’s the power button?”