The strong interaction, also known as quantum chromodynamics (QCD), is mediated through the gluons and is responsible for the formation of hadrons made up of a pair of quark and anti-quark (mesons) or alternatively, three quarks (baryons). QCD is responsible for the confinement of quarks to these composite particles and the apparent non-existence of free quarks in nature. While it is possible to perform rather simple perturbative calculations of QCD at high energies, QCD is non-perturbative at low energies, the regime relevant for the properties of hadrons. Experimental and theoretical studies of this non-perturbative regime and the detailed properties of various hadrons are intensely performed in order to better understand the complete nature of QCD.
Before the universe cooled off sufficiently for hadrons to form a particular phase of matter must have existed, in which quarks and gluons were not confined, the so-called quark gluon plasma (QGP). A large experimental and theoretical effort is directed to find this phase of matter and to study the phase transition from the QGP to hadronic matter. Experiments at the CERN SPS found first evidence for this phase of matter. Additionally, the investigation of hadronic matter at high temperature and density will allow one to draw conclusions about the hadronic interactions and the effect on those interactions by the surrounding medium. The properties of the QGP are being studied at RHIC in Brookhaven, U.S.A. and further experiments will be performed at the LHC at CERN. Hadronic matter at high temperatures and densities is also studied at the Gesellschaft für Schwerionenforschung GSI in Darmstadt.
Neutrons and protons, the building blocks of atomic nuclei, are the lightest baryons. The interaction between nucleons bound in nuclei differs from the interaction between free nucleons and thus reflects their composite nature. As a result one can describe the properties of nuclei only through the use of "effective" interactions. It is a major goal of low energy nuclear physics to base this effective description of nuclei on a more fundamental basis by bridging the gap between QCD and the effective nucleon-nucleon interaction. Experimental and theoretical efforts in nuclear physics are thus aiming to understand all components of the effective interactions by investigating nuclei at the extremes of temperature, angular momentum and proton-to-neutron ratio/isospin.
Besides the strong interactions the weak interaction plays a particular important role in nuclei, since it determines the rate of beta-decay, for example the lifetime of a free neutron. It is therefore of great importance for the nuclear burning in stars, like our sun, and the synthesis of the elements, our world consists of. Many nuclear reactions and nuclear properties that are relevant for various astrophysical processes are investigated in the laboratory by the use of stable as well as radioactive ion beams.
New accelerator facilities that provide beams of short-lived radioactive ions will have a large impact for the study of the isospin dependence of the interaction and the study of astrophysical processes. Such facilities are e.g. operational at REX-ISOLDE, CERN, GSI Darmstadt and future facilities such as the GSI upgrade and MAFF in Munich will extend the reach of such studies.
Modern research in particle and nuclear physics has become closely interrelated. Recent results on the properties of neutrinos are just one example. Work at the forefront of this field requires experiments at large research centres and in international collaborations as well as a close collaboration between theoretical and experimental groups.
At the Physik-Department several groups of scientists are leading theoretical and experimental research activities in particle and nuclear physics. The experimentalists use local facilities, like the research reactor FRM-II in Garching or the tandem accelerator as well as international research centres, like CERN at Geneva, the Gran Sasso underground laboratory in Italy, the research reactor at ILL Grenoble, and the heavy-ion accelerators at the GSI Darmstadt. The theoretical groups have collaborations with the theory groups in CERN, Fermilab, ICTP Trieste, ECT Trento and different groups at universities world wide. All these activities are coordinated and partially financed by the newly formed Maier-Leibnitz Laboratorium, by the "Sonderforschungsbereich" on Astro-Particle Physics, and by various grants from state, federal and European agencies. The campus "Forschungsgelände Garching" offers also the possibility of close co-operation with colleagues from the LMU, four Max-Planck-Institutes (plasma physics, astrophysics, extraterrestric physics, quantum optics), other faculties of the TUM, and the Walter-Meissner Institut für Tieftemperaturphysik der Bayerischen Akademie der Wissenschaften.