CBM progress report 2007

This report documents the activities within the CBM project in 2007. Significant progress has been made in the optimization of the simulation software, the layout and development of detectors, the design of front-end electronics, and the concepts for data acquisition. The simulation and analysis routines have been completely integrated into the software framework (FAIRoot and CBMroot), and can be used now easily by users outside GSI. A breakthrough has been achieved in the development of fast algorithms for track and vertex reconstruction which have been improved in speed by a factor of 105. These fast routines permit to perform high-statistics simulations for detailed detector layout optimization. Full event reconstruction based on realistic detector properties and particle multiplicities as given by microscopic transport models are routinely used in the feasibility studies. A version of the Silicon Tracking System is now implemented in the simulation software comprising 8 detector layers based on microstrip technology only, including the readout cables, and the mechanical detector structure. The studies of open charm detection have been extended to Ds+ and Λc, taking into account a realistic layout of the Silicon Pixel Microvertex detector. The identification of electrons has been optimized by improved ring recognition algorithms and transition radiation simulations. The Ring Imaging Cherenkov (RICH) detector has been redesigned, resulting in a reduction by a factor of two in mirror size and number of readout channels without reducing the pion rejection capability. The muon detection system has been optimized with respect to the number of detector layers. The muon simulations take into account detector inefficiencies and a segmentation of the muon chambers into pads according to a nominal occupancy of 5% for central Au+Au collisions. Studies for a dimuon trigger show promising results. Radiation dose simulations using the FLUKA transport code have been started. A new generation of pixel sensors for the Microvertex detector (MVD) with fast read-out architecture has been tested with pion beams at CERN. The tolerance of the sensors to non-ionizing radiation has been improved, and the construction of a MVD demonstrator has been started. The first double-side microstrip sensors have been built and will be tested. Prototype MWPCs for the measurement of transition radiation have been tested and optimized for high rate capability. Prototype staw-tube tracker modules have been built and tested. The n-XYTER readout ASIC was characterized in various test benches and is now ready for deployment in detector and beam tests in 2008. The design work on the CBM-XYTER, a radiation-hard second-generation readout ASIC for Silicon and fast gas detectors, has started in 2007. The FEE development for the RPC-TOF system saw two major milestones in 2007: the preamplifier-discriminator chip PADI was successfully tested, and the preparatory studies of several time-to-digital converter buildings blocks were concluded with the design choices for the first full system chip to be developed in 2008. Within the development of a future data acquisition system, the scalability of high-throughput event building was demonstrated on a 110 node cluster. A very important milestone will be the proton beam test of Silicon microstrip and gas detectors read out by n-XYTER ASICs at GSI end of September 2008. (orig.)