In order to gain a better understanding of the dynamics inside the nucleon and of the non-perturbative regime of QCD, the nucleon excitation spectra and the properties of nucleon resonances are investigated. An essential experimental tool to achieve this goal is the study of different photoproduction reactions. Partial wave analyses are performed in order to obtain information about the...
The talk will give an overview of the current and planned research program of the A2@MAMI collaboration. Our research program utilises the intense energy-tagged real photon beam provided by the Mainz/Glasgow tagger in conjunction with the Crystal Ball/TAPS calorimeters, ancillary charged particle detector systems and a range of polarised and unpolarised cryogenic target systems. This...
Baryon spectroscopy is an essential tool in the study of nucleon resonances. The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of polarization observables. The N* program at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) includes experimental studies with linearly- and circularly-polarized tagged-photon beams, longitudinally- and...
We give an overview of (some of) the different analysis tools and PWA approaches used to extract the spectrum of nucleon and Delta states from experimental data. Differences and similarities, e.g. in the construction of the amplitude or the data base, will be illustrated.
In addition, we show recent results of the Jülich-Bonn model, a unitary dynamical coupled-channel approach, and discuss the...
Exploring time like transitions in pp and pi--p reactions with HADES
Piotr Salabura for the HADES collaboration
Radiative transition of an excited baryon to a nucleon with emission of a virtual massive photon decaying to electron-positron pair (R->Ne+e- Dalitz decays) provides important insight into baryon-photon vertex at low q2 =(me+e-)^2 in time-like region. A prominent enhancement...
Photoproduction of kaons can be regarded as the "golden channel" in the resonance region because of the opportunity to measure combinations of beam, target and recoil polarization. This talk will look at the impact of the recent results from CLAS and elsewhere, and in particular will describe the possibility of determining the weak decay parameter of the $\Lambda$. This study complements a...
