Elementary Particle and Nuclear Physics

Subject Cataloge

Elementary Particle Physics
	Basic Physics: Astro-Particle Physics Dark Matter Fundamental Symmetries Grand Unification of Forces Neutrinos Particle Physics with Neutrons Physics of High Energy Colliders Supersymmetry The Standard Model Ultracold Neutrons Weak Decays of Mesons
Nuclear and Hadronic Physics
	Basic Physics: Effective Field-Theories Mesons and Nucleons Matter under Extreme Conditions Nuclear Astrophysics Nuclei at the Extremes Quarks and Gluons Reactions with Rare Isotopes Strong Interaction Structure of Hadrons and Nuclei
	Applied Physics: Applications of Nuclear Methods in: Medicine Biology Environment Food Archeology Development of Instrumentation Positron-Emission-Tomography (PET)
	Applications of Neutrons: Activation Analysis Silicon Doping Radiography and Tomography Tumour Therapy Production of Radioisotopes

 

Research in Elementary Particle and Nuclear Physics

Particle and Nuclear Physics are concerned with the elementary building blocks of matter and the fundamental symmetries and interactions governing the foundations of our world.

Fundamental particles, the Standard Model, and beyond

We know today that the matter around us is built of point-like objects, quarks and leptons with an experimental upper limit for their size of 10-18m. A total number of six quarks, six anti-quarks as well as six leptons and six anti-leptons have been established experimentally. These fundamental building blocks are arranged in three "families" and we have convincing arguments that this set of families is complete. The behaviour of these elementary particles is governed by four fundamental interactions, namely gravitation, electromagnetic, weak and strong interaction. The interactions between particles are meditated by so-called field bosons, which are the graviton, photon, W- and Z bosons, and the gluon, respectively.

The number of particles and corresponding anti-particles created during the "big-bang" was equal and most particle/anti-particle pairs annihilated. However, a very small imbalance, or spontaneous symmetry breaking, resulted in a small excess of the matter of today's universe.

Modern theoretical and experimental research in particle physics has succeeded to unite the electromagnetic, weak and strong interactions into a unified scheme, called the Standard Model, which is able to describe a large set of experimental data on the properties of elementary particles and simple composites thereof. One of the priorities of this field is the search for the so-called Higgs-Boson, which is thought to be responsible for the masses of the elementary particles.

The Standard Model has many parameters for which values cannot be predicted within the framework of the model and therefore have to be introduced empirically. This shortcoming, together with other theoretical arguments, makes an extension of the Standard Model necessary. Experimental evidence of Physics beyond the Standard Model was only recently provided by the observation of neutrino oscillations, which prove that neutrinos have mass, contrary to the fact that neutrinos are massless within the Standard Model. There are other indications from astro-particle physics that so-called "cold dark matter" exists, requiring the existence of new particles, which are not part of the Standard Model. Due to these facts the search for physics beyond the Standard Model is a major priority of modern experimental and theoretical particle physics.

Future experiments at Fermilab in the U.S. and the LHC at CERN will be able to study the Higgs Boson and establish more physics beyond the standard model.

Hadrons and Nuclei

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.

Activities of the Department

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.

At this point we provide a compact overview of the theoretical groups (Profs. Buras, Feldmann, Ibarra, Brambilla, Jäger und Weise) and experimental groups (Profs. von Feilitzsch, Krücken, Fabbietti, Bishop, Abele, Fierlinger, Lachenmaier, Oberauer, Paul, Schreckenbach, Zimmer) and their activities in particle and nuclear physics. More detailed descriptions of these research activities can be found in the subsequent sections of this document.

• The group of Prof. Buras (T31) studies weak decays of mesons with the aim to test the Standard Model and its possible extensions, like supersymmetry, at very short distance scales and investigates the violation of symmetry of matter and anti-matter.

• The group of Prof. Ibarra (T30d) investigates electro-weak interactions in the Standard Model and it extensions with an emphasis on neutrino physics, the Higgs-mechanism, unified theories, astro-particle physics and cosmology.

• The group of Prof. Ratz (T30e) investigates physics beyond the standard model. Topics include unified theories, in particular string compactifications, supersymmetric theories, neutrino physics, astro-particle physics and cosmology.

• The group of Prof. Brambilla (T30f) investigates QCD and Strong Interactions and  studies Effective Field Theories and Renormalization Techniques with applications to Particle Physics and Nuclear Physics.

• The group of Prof. Jäger

• The group of Prof. Weise (T39) investigates complex systems of quarks and gluons (hadrons, nuclei, matter under extreme conditions of temperature and density) on the basis of Quantum Chromodynamics, the theory of the strong interaction.

• The group of Prof. von Feilitzsch (E15) investigates the basic properties of neutrinos with the Gallium Neutrino Observatory and the BOREXINO experiments and develops the low-temperature detector CRESST for the search for dark matter.

• Die Gruppe von Prof. Lachenmaier

• The group of Prof. Krücken (E12) studies the properties of exotic nuclei, using REX-ISOLDE at CERN, AGATA, and MAFF at the FRM-II, and of hadrons in dense nuclear matter, using HADES at GSI, and applies nuclear methods to other fields.

• Die Gruppe von Prof. Fabbietti

• Die Gruppe von Prof. Bishop

• The group of Prof. Oberauer (E15) works on neutrino spectroscopy and neutrino oscillations using the BOREXINO detector in Gran Sasso and is involved in the CAMEO project for the investigation of the double beta decay.

• The group of Prof. Paul (E18) studies the internal properties of nucleons and mesons using the COMPASS experiment at CERN and is involved in building the Ultra Cold Neutron Source at the FRM-II for the investigation of the lifetime of the neutron.

• Die Gruppe von Prof. Abele

• Die Gruppe von Prof. Kienberger

• The group of Prof. Schreckenbach (E21) searches for a possible violation of the time reversal symmetry in the free neutron beta decay using the TRINE experiment at the ILL, Grenoble.

• The group of Prof. Zimmer (E18) investigates the neutron beta decay to study the electro-weak interaction and test the Standard Model at the Ultra Cold Neutron source and a strong cold neutron beam at the FRM-II.