The theory group studies the strong interaction at low and medium energies. The activities focus on the theoretical interpretation of the experiments at MAMI and at other accelerator facilities. Beside analytical methods like effective field theories and dispersion theory, numerical simulations of Quantum Chromodynamics on the lattice are applied.

### Research Topics

**Hadron structure and meson production:
** The basic observables for the understanding of the structure of the nucleon and its excited states are form factors, structure functions and parton distributions. The theoretical study of these observables are the basis for the interpretation of the experiments at MAMI, JLab, COMPASS as well as for future projects like PANDA.

**Flavour Physics:
** The calculation of weak hadronic matrix elements with lattice QCD is a central component for the determination of the elements of the CKM-matrix, and the study of CP violation in the Standard Model, as well as for searches for physics beyond the Standard Model from precise measurements of hadron lifetimes and branching fractions.

**QCD at finite temperature and density:
** Experimental studies made to assess where our theoretical understanding of nature has its limits, and where possibly so far unobserved new worlds of matter are waiting to be discovered and understood, are complemented by calculations in lattice QCD.

**Hadronic contributions to the anomalous magnetic moment of the muon:**

The anomalous magnetic moment (g-2) of the muon has been measured with extremely high precision. A similarly accurate theoretical prediction, which is needed to probe the limits of the Standard Model in the leptonic sector, requires a thorough understanding of the hadronic contributions to (g-2) from non-perturbative QCD.