In Goethe´s renowned play “Faust” polymath Heinrich Faust poses the question “whatever holds the world together in its inmost folds”. In his search for an answer he even commits himself to the realm of magic. Lilian Witthauer, particle physicist from Basel, deals with this same big exact question in her doctoral thesis. She found her answers not with the help of magic but through elaborate experiments with particle accelerators. As a reward for the superb quality of her scientific work she received the CHIPP Prize 2015 on July 29th 2015.
For many people the mentioning of particle physics automatically triggers a connection to the big particle accelerator LHC at CERN. However, particle physics is not only practiced in Meyrin close to Geneva but practically at all universities in Switzerland. Furthermore not all research in physics is focused on high-energy physics like at CERN. Scientists at other places work with great diligence on low-energy and medium-energy physics as well as neutrinos and astroparticles.
Scientific research at the University of Basel again has a very special focus. The team of scientists around Professor Bernd Krusche explores strong interaction with methods that are unique in all of Switzerland. They are exploring strong interaction, one of the four fundamental forces of nature, beside electromagnetism, gravity and weak interaction. The scientists from Basel try to understand how the strong interaction manages to “glue” three quarks into a proton or a neutron and thereby provide nuclear stability. In other word, they are striving to find out – to speak with Goethe´s Faust – “whatever holds the world together in its inmost folds”.
Giving a practical understanding of physics
In order to answer this obviously big and fascinating question the expertise of one person is not sufficient, it demands the scientific enthusiasm of a whole team. Lilian Witthauer (29), who grew up in Basel and Flüh, is part of this team. Lilian was not born as a particle physicist. At school she was interested in art but from early on also in science. Later on as a student at the Leonhard-High School in Basel her female physics teacher sparked her further interest for this subject. “As part of the physics honors class we visited a nuclear power plant and worked with radioactive sources. That way our teacher gave us a practical understanding of physics,” Witthauer remembers.
Lilian Witthauer received her Bachelor and her Masters Degree from the University of Basel, focusing on experimental physics. Here she also connected with the research team of Bernd Krusche. Scientists in his group are analyzing strong interaction by examining the excitation spectrum of nucleons (protons and neutrons). This is the field that Lilian Witthauer picked as the topic of her doctoral thesis, which is near completion. For her scientific achievement she was awarded the CHIPP Prize 2015 in the Château de Bossey in the North of Geneva. The CHIPP Prize is awarded annually by the Swiss Institute of Particle Physics (CHIPP), the umbrella organisation of particle physics, to honor the excellent work of a young researcher.
The secret of Eta-Mesons
One way to examine the excitation spectrum of protons and neutrons is to shoot photons onto them. This process will produce nucleon resonances and subsequently will make it decay into different particles. In her doctoral thesis Lilian Witthauer examined one possible decomposition: the case in which a photon is shot onto a neutron (or proton) and makes it decay into a neutron (or proton) as well as an Eta-Meson. Eta-Mesons consist of a quark-antiquark pair. They are unstable, meaning that they can only be studied for a very short time before they immediately decay.
Repeatedly Lilian Witthauer spent several weeks in Bonn and Mainz to carry out the experiments for her doctoral thesis. In both German cities the scientist from Basel could work with the specific type of electron accelerator that she needed for her experiment. The machines use alternating electromagnetic fields to accelerate particles. The Bremsstrahlung (braking radiation) produced onsite consists of light particles (photons), which scientists make collide with a target. This target can consist of hydrogen (which contains one proton in its nucleus) or deuterium (with a nucleus containing one neutron and one proton). With the help of this experimental set-up, experimental physicists can cause a collision of photons with protons or neutrons. Lilian Witthauer selected those types of decay that produced an eta-meson.
Results for better theories
Why did she undergo such an effort? The theory of quantum chromodynamics (QCD) already provides an excellent description of strong interaction. “True, pertubative QCD calculations deliver good predictions in high energy levels,“ explains the physicist from Basel. “However, when applying low energy levels you need a different approach, for example phenomenological models or data-intensive methods that require a lot of calculation in order to describe nature adequately. My research provides theoretical physicists with an experimental foundation that helps them to develop models to describe strong interaction. The decay of the Eta-Meson is especially interesting because it allows only specific resonances which are as result easier to examine.”
In Bonn and Mainz Lilian Witthauer made an interesting discovery. The stimulated protons and neutrons reacted differently when sending out an Eta-Meson. “Thanks to my experimental results I can exclude certain models that were developed to explain strong interaction,” Witthauer says. “As soon as my data gets published theoretical physicists can optimize their studies and models once again.”
Interest in cancer research
Lilian Witthauer´s scientific work contributes to the understanding of the world. She is an enthusiastic researcher and would like to continue working in this field after her final exams. “I would like to work in a profession that gives meaning to what I have done so far – for example by applying it to humans,” says the scientists who in her spare time loves running, drawing and taking photographs. Parallel to her basic research she achieved a postgraduate diploma in medical physics at the ETH Zurich. There she got interested in cancer therapies. “New technologies are extremely important in this field. I would love to make a connection between basic research and practical application”, she says.
However, now is the time to enjoy her latest award. It is the second official recognition of her scientific work. Earlier in her career the PhD student at the University of Basel already received a Dreyfus-scholarship. “The CHIPP-award is a great honor and a recognition of my work”, Lilian Witthauer says.“ It also grants nationwide acknowledgment to our physics research at the University of Basel.”
Benedikt Vogel (published June 29th 2015)
See two scientific publications by Lilian Witthauer (Links)
The CHIPP Prize is to reward annually the best PhD student in Experimental or Theoretical Particle Physics. In the evaluation, emphasis will be given to the quality of PhD scientific work and to its relevance within the student's research group, as well as to novel ideas brought up by the candidate.Image: CHIPP, Switzerland
The experimental detection of dark matter is one of the great challenges of current fundamental research in physics. This year’s prize of the Swiss Institute of Particle Physics (CHIPP) is awarded to the physicist Dr. Johanna Gramling for her latest contributions to the search for this mysterious component of matter.Image: private
The prize of the Swiss Institute of Particle Physics (CHIPP) 2016 goes to Mohamed Rameez. The 27-year-old neutrino researcher who just has earned his PhD at the University of Geneva has been awarded for his outstanding contributions to the IceCube Collaboration.Image: Bjarne Sorensen