Measurement of eta photoproduction on the proton from threshold to 1500 MeV

Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.Comment: 18 pages, 14 figures, 4 tables Submitted to EPJ

Optimization of hybrid polymer materials for 2PP and fabrication of individually designed hybrid microoptical elements thereof

In the last decade, two-photon polymerization (2PP) has gained increasing interest for the production of individually shaped 3D structures. For the successful implementation of 2PP within a production chain for the industrial manufacturing of optical microstructures, advanced material properties of the photo polymer are required. The usable laser dynamic range, shape accuracy as well as surface roughness play a crucial role. In this publication, we present the results of an iterative optimization process aiming at a material applicable for 3D structures written by 2PP. The special focus here lies on the influence of the photo initiator and stabilizer on the usable laser dynamic range and shape fidelity. The application of the optimized photo polymer for the production of a complex prism array, which could be used as master mold, is also shown

Neutron detection efficiency of BGO calorimeter at GRAAL

Experimental results on the neutron detection efficiency of the GRAAL BGO calorimeter obtained from a study of gamma p -> pi(+)n reaction are reported. Pulse height spectra were measured for neutron energies from 80 to 650 MeV. A comparison of the experimental data with a GEANT-based simulation is presented. (c) 2006 Elsevier B.V. All rights reserved

New experimental and simulated results on nuclear media effects in meson photoproduction off nuclei

New experimental approach to study meson photoproduction in nuclei is discussed. It is based on the measurement of the recoil nucleon as a tagger for identification of the initial step of reaction. Propagation of mesons and nucleons within a nucleus is described by the Intra-Nuclear Cascade (INC) model. Simulations and preliminary experimental data for the deuteron target obtained at GRAAL are presented. (c) 2008 Elsevier B.V. All rights reserved