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The search for a quasi bound η meson in atomic nuclei is reviewed. This tentative state is studied theoretically as well as experimentally. OA gold

The past year 2006 has been a very successful one for the institute: first off, a major milestone has been achieved with the in-time installation of the WASA detector at an internal target station of COSY and its subsequent commissioning. WASA-at-COSY is ready to take data and the collaboration is looking forward to its first data production run, approved by the COSY-PAC and scheduled for spring 2007. Furthermore, after very productive scientific programs, the internal experiment COSY-11 and the external beam experiments at BIG KARL have finished their data taking phases, and are now completing the analysis of the existing data. The following highlights top the list of the important scientific results: • Pentaquark studies: the TOF-collaboration has very carefully analysed their dedicated high-statistics data sample, and did not find a signal for the $\circleddash^{+}$(1540). This finding has been supported by the ANKE-collaboration in a different final state. • Bound $\eta$-nucleus states: data with unprecedented precision for the $^{3}He\eta$ system have been obtained both at ANKE and at COSY-11 in the d p-reaction, exploiting the unique possibilities at the internal COSY beam during the ramp-up of the energy. The very rapid rise of the total cross section close to threshold implies a very large $^{3}He\eta$ scattering length and hence the presence of a quasi-bound state extremely close to threshold. • Hyperon-nucleon interactions: chiral effective field theory has successfully been applied to the interactions between nucleons and hyperons. This paves the way to a model-independent approach of strange quark effects in nuclei. • Accelerator studies: the COSY accelerator has been used for spin manipulations of a polarized deuteron beam, and clear indications for a deuteron spin resonance have been obtained. All results mentioned have recently been submitted for publication. More details and further results can be found in the main text. In addition to WASA, the two other major installations continue to be developed further: [...]

We present the results of a Bayesian analysis of a Regge model to describe the background contribution for K+ Lambda and K+ Sigma0 photoproduction. The model is based on the exchange of K+(494) and K*+(892) trajectories in the t-channel. We utilise the Bayesian evidence Z to determine the best model variant for each channel. The Bayesian evidence integrals were calculated using the Nested Sampling algorithm. For different prior widths, we find decisive Bayesian evidence (\Delta ln Z ~ 24) for a K+ Lambda photoproduction Regge model with a positive vector coupling and a negative tensor coupling constant for the K*+(892) trajectory, and a rotating phase factor for both trajectories. Using the chi^2 minimisation method, one could not draw this conclusion from the same dataset. For the K+ Sigma0 photoproduction Regge model, on the other hand, the difference between the evidence integrals is insufficient to pinpoint one model variant., Comment: 13 pages, 4 figures

The IKP has achieved a strategic success in 2009: the proposal of the IKP for funding in the Research Program Physics of Hadrons and Nuclei, defined in the framework of the Program Oriented Funding of the Helmholtz centers, has been evaluated in February with great success. This decision guarantees the funding of IKP as well as those parts of ZAT and ZEL participating in the proposal for the time period from 2010 till 2014. The following outstanding experimental results have been obtained: • The WASA at COSY collaboration has used the pd $\rightarrow$ $^{3}$He $\eta$ reaction to accumulate 30 million $\eta$-meson decays, obtaining clear signatures of 300 events of the type $\eta$ $\rightarrow$ $\pi^{+}\pi^{-}e^{+}e^{-}$ These data are relevant for tests of the chiral anomaly.

On July 1, the board of directors of the Forschungszentrum Jülich (FZJ) founded the$\textbf{Jülich Center for Hadron Physics (JCHP)}$. The main goal of the JCHP is to coordinatethe hadron physics activities at the FZJ for the FAIR project. This includes activitiesat the Institute for Advanced Simulations (IAS), the Institut für Kernphysik (IKP), theZentralinstitut für Elektronik (ZEL) and the Zentralabteilung Technologie (ZAT). Withinthe Helrnholtz Association (HGF) research field $\textit{Structure of Matter}$, the FZJ operatesthe COSY facility and has achieved an excellent international reputation due to the closecooperation between accelerator physicists, experimentalists and theoreticians. In cooperationwith ZEL and ZAT, the IKP is in charge of the construction and operation of theHigh Energy Storage Ring HESR and makes a strong contribution to the PANDA detectorand its physics. PAX is exploiting methods to effectively polarize (anti-)protons for apossible future upgrade at FAIR.The FZJ operates the JUGENE/JSC supercomputer and hosts the John von Neumann institutewhich develops lattice gauge simulation calculations of quantum chromodynamics(QCD) and hadron structure. The JCHP coordinates these activities by establishing a directconnection between the lattice QCD simulation groups and hadron physicists. Moreover,the infrastructure provided by the IAS for mass storage, presently used for COSYdata, may handle FAIR data and perform Monte Carlo simulations of HESR experiments.External users are essential for the success of an accelerator complex, therefore, the JCHPfacilitates the contact of external users with the FZJ and supports external activities in thefield of hadron physics. Presently an initiative of the universities within North-RhineWestfalia and the FZJ, called NRW-FAIR, is forming to coordinate their FAIR-relatedactivities.Starting December 1, 2008, the IKP-3 theorists also work in IAS-4, the strong interactionphysics branch of the Institute for Advanced Simulations (IAS). The Virtual Institute $\textit{Spinand Strang QCD}$ has presented its first results on June 1 in Ferrara.A Helmholtz-Russia Joint Research Group, the first one in Jülich, will receive fundingfrom the Impuls- und Vernetzungsfond of the Helmholtz Association and from the RussianFoundation for Basic Research for the next three years. In a joint effort of the FZJ,the Budker Institute in Novosibirsk, TU Dortmund and JINR Dubna methods for electroncooling in the MeV region, relevant for FAIR, will be developed.The IKP has initiated a cooperation with the 100-TW laser facility at the HeinrichHeineUniversity Düsseldorf. The potential of new particle acceleration technologies withlimited-mass targets will be explored, exploiting the know-how on frozen-pellet targetsgained at the IKP. The year 2008 has seen important experimental and theoretical progress: [...]

The year 2005 has been a challenging one for the institute: as a consequence of the “mixed results” of the first review in February 2004 within the Research Programme “Physics of Hadrons and Nuclei” in the Research Field “Structure of Matter” of the Helmholtz Centres, IKP was faced with substantial cuts in resources for 2005. An even more serious threat ensued with possible further reductions for the years 2006 – 2009, depending, however, on the outcome of an “in-depth” evaluation of the IKP activities. The review on “COSY and FZJ contributions to FAIR”, conducted by an international committee, and headed by Peter Paul (BNL, USA), took place on two days in April 2005. IKP presented its strategy for the further use of COSY and, in close collaboration with GSI (Darmstadt), the cooperation towards the construction of the FAIR facility. In its report, issued later last year, the committee almost fully supported our plans, and as a result and the financial agreements, which have been negotiated in the meantime, we now have a solid basis for the remainder of the first funding period (2006 – 2009). — I would like to take this opportunity to thank all who contributed to this great success in one way or the other. One of the explicit recommendations of the committee was to give green light for the relocation of the WASA detector from CELSIUS (Uppsala, Sweden) to COSY. The detector dismount at TSL and transfer to FZJ was completed in 2005, and we are now in the process of installing WASA at an internal target station of COSY — more details are given in the main text. Commissioning of WASA is scheduled to begin in the second half of 2006 and first experiments are expected to start in 2007. In connection with the WASA-at-COSY project, the IKP had decided to reduce the amount of COSY beamtime for users in 2005 by about 2000 hours. The increased downtime is needed to install WASA in the COSY ring, but also has the positive side-effect that the cost-savings will be used to finance necessary maintenance and upgrades of WASA detector components and electronics. This was part of the financing concept which has been worked out between the IKP directorate and the FZJ board of management. On the scientific frontier, IKP has made a number of important contributions (details can again be found in the main text): • The ANKE collaboration has found indications for a heavy hyperon state Y$^{0*}$(1480) in the analysis of pp $\rightarrow$ pK$^{+} \pi$X at a beam momentum of 3.65 GeV/c. • The GEM collaboration has determined the mass of the h meson with unprecedented accuracy, exploiting the reaction pd $\rightarrow$ $^{3}He \eta$ and simultaneously pd $\rightarrow$ t$\pi^{+}$ at the BIG KARL magnetic spectrometer (see cover picture and corresponding article). • At COSY the efficiency for flipping the proton spin by means of a small rf dipole has been pushed to more than 99.9%. • The intensity of the polarized ion source for H$^{−}$ was raised to 50$\mu$A, thus doubling its original specification. The involvement of the IKP in the FAIR project to be realized at the GSI was fully honored by the committee. Our efforts are focused on the design and construction of the High Energy Storage Ring (HESR) and significant contributions to the PANDA detector. We are dedicated to make this endeavor a success being aware of its great potential to advance hadron physics and connected fields during the next decades. We have been able to meet the challenges of 2005 not only due to our own efforts, but because we could rely on the support and advice of many people. I like to express our gratitude to all of them, the colleagues from the infrastructure of our Research Center (FZJ) in particular ZAM, ZAT, and ZEL, the people from the universities and research centers from Germany and all over the world and, last but not least, the CANU community.

Nucleon-nucleon interactions and hyperon nucleon interactions are study in three body final state with one being a meson. In addition to final state parameters possible resonances in the two baryon states are of interest.

At its last meeting the COSY User Association, CANU, asked the community to putforward their interests in the physics relevant to the spectrometer `$\textbf{Big Karl}$' at COSY.In response to the charge of CANU, a `brainstorming meeting' was held April 10-11, 2000to determine whether there is the enthusiasm and potential justifying the future operationof the facility. The meeting attracted 35 participants from 10 national and internationalinstitutions to present and discuss a variety of topics related to future experiments at BigKarl.Before summarizing details of the meeting, a short description of the spectrometer facilityBig Karl is given. The facility is essentially a new instrument using refurbished dipolemagnets from its predecessor. The large acceptance quadrupole magnets and the beamoptics are new. Big Karl has a design very similar as the focussing spectrometers at MAMI(Mainz), AGOR (Groningen) and the high resolution spectrometer (HRS) in Hall A atJefferson Laboratory with $\Delta$E/E = 10$^{-4}$ but at some lower maximum momentum. Thefocal plane detectors consisting of multiwire drift chambers and scintillating hodoscopesare similar. Unlike HRS, Big Karl still needs Cerenkov counters and polarimeters in itsfocal plane; detectors which are necessary to perform some of the experiments proposedduring the brainstorming. In addition, BIG KARL allows emission angle reconstructionvia track measurements in its focal plane with high resolution.In the following the physics highlights, the proposed and potential experiments aresummarized. During the meeting it became obvious that the physics to be explored atBig Karl can be grouped into five distinct categories, and this summary is organizedaccordingly.