120484753
The front-end readout electronics for the P̄ANDA Focussing-Lightguide Disc DIRC
One of the key detectors of the upcoming ANDA experiment for particle identification will be the Focussing-Lightguide Disc DIRC, based on a novel detector technique. It will use a fused silica disc as a solid radiator to generate Cherenkov light by the passing of charged particles. These photons will be transported by total-internal-reflection to the rim, where LiF crystals will be used to perform dispersion corrections. Focussing lightguides will map propagation angles to spatial positions on the surface of photon detectors. Fast single photon detection devices will be used to measure azimuthal angles and spatial positions, which can be used to reconstruct kinematic properties of the passing particles. The expected average interaction rate of 20 MHz yields a photon detection rate of 1.3 MHz, as it is foreseen to use 128 MCP-PMT, each with 32 channels, for continuous readout. Moderate timing resolution of 300 ps improves signal from noise separation. The readout design requirements for the Focussing-Lightguide Disc DIRC will be introduced. The current candidate for implementation of the front-end readout electronic system will be described and several alternative readout scenarios will be discussed. Finally, a summary and an outlook for further developments and tests will be given.
120848137
The bar PANDA focussing-lightguide disc DIRC
ANDA will be a fixed target experiment internal to the HESR antiproton storage ring at the future FAIR complex. The ANDA detector requires excellent particle-identification capabilities in order to achieve its scientific potential. Cherenkov counters employing the DIRC principle were chosen as PID detectors for the Target Spectrometer. The proposed Focussing-Lightguide Disc DIRC will cover the forward part of the Target Spectrometer acceptance in the angular range between 5° and 22°. Its design includes a novel approach to mitigate dispersion effects in the solid radiator of a DIRC counter using optical elements. The dispersion correction will enable the Focussing-Lightguide Disc DIRC to provide pion-kaon identification for momenta well above 3.5 GeV/c.
117724729
Particle spectra and interferometry results from NA44
5947662
Emission of unstable clusters from hot Yb compound nuclei
Neutrons and isotopically resolved light charged particles have been detected in coincidence with evaporation residues produced in the reaction E/A=11 MeV {sup 60}Ni+{sup 100}Mo. Multiplicities of evaporated particle-unstable clusters have been determined from correlations in the emission of these light particles. The decay of the short-lived {sup 5}He and {sup 8}Be (E{sup *}=3.04 MeV) states was found to be affected by the Coulomb field of the compound nucleus in accordance with theoretical estimates. The contributions to the measured kinetic-energy distributions of stable fragments from the sequential decay of the unstable clusters was examined. Overall, the contributions from secondary fragments do not greatly influence the spectral shapes and specifically the location of the spectral peaks are not significantly shifted down in energy due to the presence of these secondary fragments. Therefore contrary to the suggestion of Charity [Phys. Rev. C 56, 873 (1997)], the lower peak energy of the experimental {alpha}-particle spectrum as compared to standard statistical-model calculations cannot be attributed to sequential {alpha} particles from {sup 5}He and other clusters. Only for the extreme ''subbarrier'' regions of the {alpha}-particle, deuteron, {sup 6,7}Li, and {sup 8}Be spectra was the sequential contribution found to be dominant. Statistical-model calculations incorporating large initial deformationsmore » are shown to provide enhancements in the yield of low-energy fragments which are roughly appropriate for all the detected isotopes. This suggests that the origin of the sub-barrier enhancements may be a result of evaporation from highly deformed systems which are either produced dynamically during the fusion process or by thermal shape fluctuations.« less
119390799
Caloric curves and nuclear expansion
Nuclear caloric curves have been analyzed using an expanding Fermi gas hypothesis to extract average nuclear densities. In this approach the observed flattening of the caloric curves reflects progressively increasing expansion with increasing excitation energy. This expansion results in a corresponding decrease in the density and Fermi energy of the excited system. For nuclei of medium to heavy mass apparent densities ~ 0.4 rho_0 are reached at the higher excitation energies.
18563301
Limiting temperatures and the equation of state of nuclear matter.
From experimental observations of limiting temperatures in heavy ion collisions we derive the critical temperature of infinite nuclear matter Tc=16.6+/-0.86. Theoretical model correlations between Tc, the compressibility modulus K, the effective mass m*, and the saturation density rho s are then exploited to derive the quantity (K/m*)1/2 rho -1/3 s. This quantity together with calculations employing Skyrme and Gogny interactions indicates a value of K in moderately excited nuclei that is in excellent agreement with the value determined from giant monopole resonance data.