High-energy-resolution inelastic electron scattering (at the S-DALINAC) and proton scattering (at iThemba LABS) experiments permit a thorough test of the nature of proposed one- and two-phonon ...symmetric and mixed-symmetric 2{sup +} states of the nucleus {sup 94}Mo. The combined analysis reveals the one-phonon content of the mixed-symmetry state and its isovector character suggested by microscopic nuclear model calculations. The purity of two-phonon 2{sup +} states is extracted.
Proton inelastic scattering experiments at energy E_p = 200 MeV and a spectrometer scattering angle of 0 degree were performed on 144,146,148,150Nd and 152Sm exciting the IsoVector Giant Dipole ...Resonance (IVGDR). Comparison with results from photo-absorption experiments reveals a shift of resonance maxima towards higher energies for vibrational and transitional nuclei. The extracted photo-absorption cross sections in the most deformed nuclei, 150Nd and 152Sm, exhibit a pronounced asymmetry rather than a distinct double-hump structure expected as a signature of K-splitting. This behaviour can be related to the proximity of these nuclei to the critical point of the phase shape transition from vibrators to rotors with a soft quadrupole deformation potential. Self-consistent random-phase approximation (RPA) calculations using the SLy6 Skyrme force provide a relevant description of the IVGDR shapes deduced from the present data
ALICE HLT High Speed Tracking on GPU Gorbunov, S.; Rohr, D.; Aamodt, K. ...
IEEE transactions on nuclear science,
08/2011, Letnik:
58, Številka:
4
Journal Article
Recenzirano
The on-line event reconstruction in ALICE is performed by the High Level Trigger, which should process up to 2000 events per second in proton-proton collisions and up to 300 central events per second ...in heavy-ion collisions, corresponding to an input data stream of 30 GB/s. In order to fulfill the time requirements, a fast on-line tracker has been developed. The algorithm combines a Cellular Automaton method being used for a fast pattern recognition and the Kalman Filter method for fitting of found trajectories and for the final track selection. The tracker was adapted to run on Graphics Processing Units (GPU) using the NVIDIA Compute Unified Device Architecture (CUDA) framework. The implementation of the algorithm had to be adjusted at many points to allow for an efficient usage of the graphics cards. In particular, achieving a good overall workload for many processor cores, efficient transfer to and from the GPU, as well as optimized utilization of the different memories the GPU offers turned out to be critical. To cope with these problems a dynamic scheduler was introduced, which redistributes the workload among the processor cores. Additionally a pipeline was implemented so that the tracking on the GPU, the initialization and the output processed by the CPU, as well as the DMA transfer can overlap. The GPU tracking algorithm significantly outperforms the CPU version for large events while it entirely maintains its efficiency.
Gamma-ray emission from the recoil particle can have a large effect on the blocking dip observed in crystal blocking experiments. We demonstrate this effect experimentally, and give a theoretical ...description based on standard chaneling theory that is in good agreement with the measurement. We discuss the implications for lifetime measurements using the crystal blocking technique.
In this work, we examine critically the relation between orbital magnetic dipole (scissors mode) strength and quadrupole deformation properties. Assuming a simple K=0 ground-state band in an ...even-even nucleus, the quantities Q(2{sub 1}{sup +}) (i.e., the static quadrupole moment) and B(E2){sub 0{sub 1}}{sub {yields}}{sub 2{sub 1}} both are described by a single parameter--the intrinsic quadrupole moment Q{sub 0}. In the shell model, we can operationally define Q{sub 0}(static) and Q{sub 0}(BE2) and see if they are the same. Following a brief excursion to the sd shell, we perform calculations in the fp shell. The nuclei we consider ({sup 44,46,48}Ti and {sup 48,50}Cr) are far from being perfect rotors, but we find that the calculated ratios Q{sub 0}(static)/Q{sub 0}(BE2) with an FPD6 interaction are often very large (very close to unity) and far from the simple vibrational limit of zero. The experimental ratios for {sup 46}Ti and {sup 48}Ti are somewhat smaller ({approx}0.75), but the {sup 50}Cr value is larger, exceeding unity. We also discuss the quadrupole collectivity of orbital magnetic dipole transitions. We find that the large orbital B(M1) strength in {sup 44}Ti relative to {sup 46}Ti and {sup 48}Ti cannot be explained by simple deformation arguments.
The IVGDR in 208Pb has been measured with high energy resolution with the (p,p') reaction under extreme forward angles and shows considerable fine structure. Characteristic scales are extracted from ...the spectra with a wavelet analysis based on continuous wavelet transforms. Comparison with corresponding analyses of B(E1) strength distributions from microscopic model calculations in the framework of the QPM and relativistic RPA allow to identify giant resonance decay mechanisms responsible for the fine structure. The level density of 1- states can be related to local fluctuations of the cross sections in the energy region of the IVGDR. The magnitude of the fluctuations is determined by the autocorrelation function. Scales in the fine structure of the IVGDR in 208Pb are found at 80, 130, 220, 430, 640, 960 keV, and at 1.75 MeV. The values of the most prominent scales can be reasonably well reproduced by the microscopic calculations although they generally yield a smaller number of scales. In both models the major scales are already present at the one-particle one-hole level indicating Landau damping as a dominant mechanism responsible for the fine structure of the IVGDR in contrast to the isoscalar giant quadrupole resonance, where fine structure arises from the coupling to low-lying surface vibrations. The inclusion of complex configurations in the calculations changes the E1 strength distributions but the impact on the wavelet power spectra and characteristic scales is limited. The level density of 1- states is extracted in the excitation energy range 9-12.5 MeV and compared to a variety of phenomenological and microscopic models. The back-shifted Fermi gas model parameterization of Rauscher et al., Phys. Rev. C 56, 1613 (1997) describes the level-density data well, while other phenomeological and microscopic approaches fail to reproduce absolute values or the energy dependence or both.
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