Professor Dr. Johannes Henn, Professor of Mathematical Physics at Johannes Gutenberg University Mainz (JGU), has been awarded one of the largest grants from the European Research Council to develop new computational methods in theoretical physics. Henn was appointed to Mainz in June 2015 by the renowned Institute for Advanced Study (IAS) in Princeton, New Jersey, USA. He is one of the leading theorists in the field of scattering amplitudes, which are required to describe experiments at particle accelerators. Henn is pursuing an innovative approach based on a better understanding of the analytical properties of scattering amplitudes. The European Research Council (ERC) is supporting the project over the next five years with an ERC Consolidator Grant of around 2 million euros.

Johannes Henn, born in Munich in 1980, began his academic career in France. In 2005, he completed a program of study at the École normale supérieure de Lyon, and in 2008 he completed his doctorate in theoretical Particle Physics at the Laboratoire d’Annecy-Le-Vieux de Physique Théorique. After a first research period as a postdoctoral researcher at Humboldt University Berlin from 2008 to 2011, Henn conducted research at the Institute for Advanced Study in Princeton until his appointment in Mainz. The IAS, where Albert Einstein once worked, is a world leader in the field of theoretical Particle Physics. “As a pure research institute, the IAS was the ideal environment to develop completely new approaches through discussions with co-workers and with time for undisturbed reflection,” explains Henn. His future research, which will be funded by the ERC grant, will build on this preliminary work.

Henn’s research area is quantum field theory. It was developed in the second half of the last century and, put simply, describes the interaction of elementary particles. Feynman diagrams, which visualize the interactions between the particles, have become established for graphical representation. In his ERC project, Johannes Henn will refine the methods of quantum field theory to enable theorists to make predictions for high-precision experiments, such as those currently underway at the Large Hadron Collider (LHC) at CERN. Of particular interest, for example, is a comparison of the theories with the actually measured properties of the Higgs boson, which was discovered at CERN in 2012 as the last elementary particle of the standard model. With the further expansion of the LHC and experiments at even higher energies, ever more precise results will be presented, which will require new calculations on the theory side.

Traditional calculation methods quickly reach their limits here. Henn’s work is therefore initially concerned with the mathematical structure of the theoretical models and their simplification, which makes it possible to apply the theory to the experiments in the first place. He himself is primarily working on understanding fundamental structures and finding efficient methods for calculating scattering processes. Scattering processes occur in accelerators such as the LHC when particles collide and are described by so-called scattering amplitudes in the context of quantum field theory. “You often find a very simple result at the end of a complicated, page-long calculation. For physicists, this is an indication of simpler relationships and new properties of the theories that have not yet been considered. The aim is then to discover new principles that simplify these and future calculations,” explains Henn. In particular, he has succeeded in demonstrating a new Technics Department for calculating Feynman integrals, which is now widely used. “If you are looking for surprising, simple structures, you often find them in quantum field theory,” explains the physicist, with instructions that the research area has developed very dynamically over the last ten years and is constantly producing new discoveries.

In the year and a half since his appointment in Mainz, Henn has built up a work group whose research is now also supported by the ERC grant. The results will ultimately also help to measure the fundamental parameters of nature, such as the interactions of the Higgs boson, with even greater precision. In addition, results are expected that will make a significant contribution to the search for completely new particles.

In February 2017, Henn and co-workers are organizing a two-week conference at the Mainz Institute for Theoretical Physics (MITP), which renowned international scientists are expected to attend at JGU. The work of the theory group is also integrated into the Cluster of Excellence “Precision Physics, Fundamental Interactions and Structure of Matter” (PRISMA), which is funded as part of the Excellence Initiative of the German federal and state governments.

The ERC Consolidator Grant is one of the EU’s most highly endowed funding measures for individual scientists. The European Research Council uses it to fund outstanding scientists at the beginning of their independent careers, i.e. usually between 7 and 12 years after their doctorate, when their own research program is being expanded. Johannes Henn is therefore one of the youngest researchers to receive this personal award. In addition to scientific excellence, applicants must demonstrate the pioneering approach of their project and its feasibility in order to receive the grant.