## Theory of Elementary Particles and Quantum Chromodynamics on the Lattice

The Standard Model of Elementary Particle Physics (SM) comprises in its description of the electromagnetic, the weak and the strong interactions those three out of the four known fundamental forces, which are relevant on the level of the constituents of matter. The theoretical basis of this model is provided by the Quantum Theory of Fields. Although the SM is experimentally confirmed with impressive accuracy until today, there are phenomena it can not or only unsatisfactorily explain. Therefore, the particle physics community is convinced that the SM has to be extended in a proper way. The search for hints at physics beyond this established model and for constraints on its possible extensions thus belongs to the most intensive activities in particle physics worldwide. A strategy, which is complementary to direct searches for New Physics at particle accelerators and in which theoretical physics plays a crucial role, consists in testing the SM and unveiling deviations from its predictions by a combination of experimental data and theoretical computations. Since the underlying physical processes involve hadrons, i.e., bound states of quarks and gluons, as initial states, the quantification of the effects of the strong interaction (Quantum Chromodynamics – QCD) becomes particularly important. This in turn includes problems, which can not be tackled by a perturbative expansion, because the QCD coupling constant increases in the low-energy, hadronic regime such that perturbation theory is no valid approximation any more there. However, the formulation of QCD on a space-time lattice offers an ab initio framework for a systematic, non-perturbative treatment of the theory by means of numerical simulations on computers.

## Main research interests and some current projects:

- Field theories on the lattice
- Precision computations of QCD and SM parameters by means of lattice QCD
- Hadron and flavour physics on the lattice, particularly heavy quark systems (charm, beauty)
- D- and B-meson decays
- Heavy Quark Effective Theory
- Non-perturbative renormalization and O(a) improvement on the lattice

Part of the projects is being conducted within the **ALPHA Collaboration** and the **CLS Cooperation** of lattice QCD research groups.