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Beiträge zur Erforschung der starken Wechselwirkung

English title Investigations of the Strong Interaction
Applicant Krusche Bernd
Number 121781
Funding scheme Project funding (Div. I-III)
Research institution Departement Physik Universität Basel
Institution of higher education University of Basel - BS
Main discipline Nuclear Physics
Start/End 01.01.2009 - 31.12.2010
Approved amount 1'192'313.80
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Keywords (17)

Struktur des Nukleons; In - Mediumeigenschaften von Nukleonen; Photonukleare Reaktionen; Niederenergie Reaktionen (nukleare Astrophysik); strong interaction; structure of hadrons; in-medium properties of hadrons; nucleon resonances; photo-nuclear reactions; photo-production of mesons; anti-proton induced reactions; ELSA-; MAMI-electron accelerators; Crystal Ball-; Crystal Barrel-; TAPS-; PANDA-experiments

Lay Summary (English)

Lead
Lay summary
The main topic of the research project is the structure of hadrons and their interactions. These are particles which participate in the strong interaction, which is one of the four fundamental forces of nature, described by Quantum-Chromo Dynamics. The best known examples are the proton and the neutron (called nucleons), which are the building blocks of atomic nuclei. Hadrons are composed of elementary particles called quarks. All hadrons known up to now belong to one of two different classes, the baryons (among them protons and neutrons), which are composed of three quarks and the mesons (instable, short lived particles), which are made of quark - antiquark pairs. Unlike any other composite system, most of the mass of hadrons is generated by dynamical effects from the interaction of the quarks. As an example, the sum of the masses of the three quarks forming nucleons, contributes only about 0.6% - 1.8% to the mass of the nucleon. This means, that more than 98% of the mass of ordinary matter arise from dynamical effects of the strong interaction. The structure of hadrons is thus intimately related to the properties of the strong interaction. Recently, due to the large progress in the field of lattice QCD and chiral perturbation theory, a much more solid connection between experimental observations and the fundamental properties of QCD started to emerge. However, up to now even the excitation spectrum of the nucleon is far from being understood. It is still out of reach for lattice calculations and quark models predict much more excited states than have been observed.Most of those states have been observed with hadron induced reactions, in particular elastic scattering of charged pions. It is thus possible that the data base is biased for states that couple only weakly to pions. However, the large progress in accelerator and detector technology, now allows to study the electromagnetic excitation of resonances via photon induced reactions, in particular photoproduction of mesons, with comparable precision, although the cross sections are much smaller. Our group is strongly involved in experiments at the Bonn ELSA (see http://wwwnew.hiskp.uni-bonn.de/cb/)and the Mainz MAMI electron accelerators (see http://wwwa2.kph.uni-mainz.de/A2/). Both experiments use tagged photon beams and state-of the art electromagnetic calorimeters for the detection of the decay products of the mesons. The availability of polarized photon beams combined with polarized targets opens a whole new field of experiments, which are highly sensitive to the properties of nucleon resonances. Our group, in particular, has initiated a very fruitful program concentrated on meson photoproduction of the (quasi)-free neutron (loosely bound in the deuteron). In addition we investigate the modifications of hadrons embedded in the nuclear medium via the investigation of meson photoproduction off (heavy) nuclear targets. In parallel to these experimental activities our group is involved in the technical developments of the PANDA detector, which will be the main working horse for the investigation of the strong interaction via proton - antiproton collisions at the planned FAIR facility at GSI in the next decade. During the last few years, we have developed key components for the front-end electronics the electromagnetic calorimeter, which is a central component of the detector. Currently, prototype construction and tests are under way and construction of the first calorimeter sections will start in 2009/2010 (see Technical Design Report for the PANDA Electromagnetic Calorimeter http://arxiv.org/abs/0810.1216v1).
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
132799 Beitraege zur Erforschung der starken Wechselwirkung 01.01.2011 Project funding (Div. I-III)
175807 Beitraege zur Erforschung der starken Wechselwirkung 01.01.2018 Project funding (Div. I-III)
117601 Beiträge zur Erforschung der starken Wechselwirkung 01.01.2008 Project funding (Div. I-III)

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