Fundamental forces and particles

In order to understand how the Universe has evolved from the Big Bang to the present and will evolve in the future, physicists are trying to track down the fundamental building blocks of nature and their basic forces among themselves. The current state of knowledge is summarized in the standard model of particle physics. Nevertheless, physicists are convinced that it is only an approximation to a more fundamental theory, because the Standard Model cannot explain some phenomena.

Tracking down the limits of the laws of nature ...

One deficit is that it does not describe gravity. To bring the gravitational interaction consistently into line with the quantum mechanical description in the Standard Model is still a great challenge in theoretical physics today.
It is also incomprehensible why the Higgs boson has a mass much smaller than that of the natural mass scale. Dark matter also cannot be explained, nor can it be explained why there is an excess of matter in the Universe over antimatter, so that ultimately life could emerge.

Physicists tirelessly search for answers. On the one hand, they collide protons at the highest possible energies and investigate the particles resulting from the collision, such as Higgs bosons, top quarks or, at best, novel particles. On the other hand, they carry out measurements of particle properties at lower energy with very high precision in order to search for deviations from the prediction of the Standard Model and thus obtain indications of a generally valid theory. In addition, the researchers want to understand the mechanism by which quarks form bound states such as the proton or a quark gluon plasma via the strong interaction, as in the early Universe.

... with combined forces

In Research Unit A (RU-A), theorists in the fields of string theory, electroweak interaction and quantum chromodynamics work closely together with researchers on experiments such as ATLAS and ALICE at CERN, the Belle II experiment in Japan and the measurement of electric dipole moments.