The Transregional Collaborative Research Centre addresses the nature and inner structure of particles called hadrons, which are subject to the strong interactions. The most familiar ones, protons and neutrons, constitute atomic nuclei and represent the visible matter of the universe.
In particular, the existence and properties of hadrons shall be traced back to the elementary forces between quarks, which are supposed to be the elementary particles of matter. Although it is commonly accepted that QuantumChromoDynamics (QCD) is the correct underlying theory to describe the very strong force between the quarks, it is practically impossible to gain solutions at energy scales typical for hadrons, even with the fastest computers available today.
In close analogy to the successful discovery of the structure of atoms, the study of the excitation spectrum by measurement of the number, energy and other properties of excited states (so called resonances), promises to reveal crucial information about hadrons. Electrons and photons (particles of light) of sufficiently high energy are ideal probes for this goal. Only recently the prerequisites for significant experiments became available. The electrons have to be accelerated to the necessary energies, extracted continuously with aligned spins and directed to a spin-polarised proton target. Finally, the particles emerging during the decay of the excited states have to be registered, identified and assigned to individual reactions by high-performance detectors in order to relate them to the resonances under study.
The ELSA accelerator facility in Bonn with its multi-GeV polarised electron beam and the development of highly polarised proton and neutron targets is one of few laboratories worldwide that fulfil these requirements. The first experiments focus on the search for theoretically predicted but experimentally missing resonances as well as the investigation of highly excited states by observation of their sequential decays with the Crystal Barrel photon spectrometer. The results shall be interpreted with and confronted to recently developed effective theories and theoretical models to gain a deeper insight in our understanding of the structure of hadrons as bound systems of strongly interacting quarks.
DFG Programme
CRC/Transregios
Completed projects
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A01 - Spectroscopy of Baryon resonances
(Project Heads
Beck, Reinhard
;
Thoma, Ulrike
)
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A02 - Partial wave analysis
(Project Heads
Sarantsev, Andrey
;
Thoma, Ulrike
)
-
A03 - Magnetic Moments of Excited Baryons
(Project Heads
Kotulla, Martin
;
Metag, Volker
)
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A04 - Multiquark states of baryons
(Project Heads
Goeke, Klaus
;
Polyakov, Ph.D., Maxim
)
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A05 - Quark model description of baryon properties
(Project Heads
Metsch, Bernard Ch.
;
Petry, Herbert R.
)
-
A06 - Baryon resonances in a finite volume
(Project Heads
Meißner, Ulf-G.
;
Rusetsky, Akaki
)
-
A07 - Baryon masses, resonances and production processes with functional methods
(Project Head
Fischer, Christian
)
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B01 - Photoproduction of mesons
(Project Heads
Klein, Friedrich R.
;
Schmieden, Hartmut
)
-
B03 - Chiral dynamics with (non)strange quarks
(Project Heads
Kubis, Bastian
;
Meißner, Ulf-G.
)
-
B04 - In-medium properties of the mesons
(Project Head
Brinkmann, Kai-Thomas
)
-
B05 - Hadrons in Nuclear Matter
(Project Head
Mosel, Ulrich
)
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B06 - Neutron properties from light nuclei
(Project Heads
Epelbaum, Evgeny
;
Hammer, Hans-Werner
;
Meißner, Ulf-G.
)
-
B07 - Coupled channels approach to photo-meson production on the nucleon
(Project Head
Lenske, Horst
)
-
B08 - Recoil polarization measurements
(Project Head
Brinkmann, Kai-Thomas
)
-
C02 - Dispersion theoretical analysis of the nucleon form factors
(Project Heads
Hammer, Hans-Werner
;
Meißner, Ulf-G.
)
-
C03 - Spin structure of the nucleon (theory)
(Project Head
Meißner, Ulf-G.
)
-
C05 - Study of QCD-dynamics in n and n' production and decays
(Project Heads
Beck, Reinhard
;
Wiedner, Ulrich
)
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C07 - Properties of flavor-singlet pseudo-scalar mesons from lattice QCD
(Project Head
Urbach, Carsten
)
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C09 - Chiral dynamics of/with instable particles
(Project Heads
Epelbaum, Evgeny
;
Krebs, Hermann
;
Meißner, Ulf-G.
)
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D01 - Polarized Solid Target
(Project Heads
Dutz, Hartmut
;
Goertz, Stefan
;
Meyer, Werner
)
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D02 - Beam and spin dynamics in a fast ramping stretcher ring
(Project Heads
Hillert, Wolfgang
;
Klein, Friedrich R.
)
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D03 - Timing and tracking for the Crystal Barrel detector
(Project Heads
Beck, Reinhard
;
Brinkmann, Kai-Thomas
;
Novotny, Rainer
)
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R01 - Integrated Research Training Group
(Project Heads
Beck, Reinhard
;
Brinkmann, Kai-Thomas
;
Epelbaum, Evgeny
)
-
Z01 - Central tasks of the SFB / Transregio
(Project Heads
Meißner, Ulf-G.
;
Thoma, Ulrike
)
