124098674
Search for new neutral gauge bosons in 1.8-TeV proton-antiproton collisions
64351367
Consumer server: A UNIX based event distributor in new CDF data acquisition system
Consumer Server is a program to handle event data and consumer trigger requests I/Os among Level 3 farm and consumer processes in CDF new data acquisition system. This program uses standard UNIX libraries and commercial network technologies to obtain higher portability. The authors describe the concept and configuration of the Consumer Server and report its performance.
119946613
Mass production of tile/fiber units for the CDF plug upgrade EM calorimeter
Abstract We have fabricated scintillating tile/fiber units for the CDF plug upgrade electromagnetic calorimeter. The total number of tile/fiber systems amounts to ∼23 000. We describe the quality control tests of scintillator plates, optical fibers, and tile/fiber units which we placed at various stages in the fabrication procedures. We have completed the production retaining the tile/fiber units which satisfy our requirements.
16684392
How rare is the bullet cluster
The galaxy cluster 1E 0657−56 has a bullet-like subcluster that is moving away from the centre of the main cluster at high speed. Markevitch et al. (2004) recently estimated a relative velocity of Vbullet= 4500+1100−800  km s−1, based on observations of the bow shock in front of the subcluster. The weak lensing analysis of Clowe, Gonzalez & Markevitch (2004) indicates that a substantial secondary mass peak is associated with this subcluster. We estimate the likelihood of such a configuration by examining the distribution of subhalo velocities for clusters in the Millennium Run, a large Λ cold dark matter (ΛCDM) cosmological simulation. We find that the most massive subhalo has a velocity as high as that of the bullet subcluster in only about one out of every 100 cluster-sized haloes. This estimate is strongly dependent on the precise velocity adopted for the bullet. One of the 10 most massive subhaloes has such a high velocity about 40 per cent of the time. We conclude that the velocity of the bullet subcluster is not exceptionally high for a cluster substructure, and can be accommodated within the currently favoured ΛCDM cosmogony.
119460856
Is Angular Momentum in an Accretion Disk Transported Inwards
The derivation of the viscosity formula of accretion disks appearing in a number of textbooks is based on a mean free path theory of gas particles. However, this procedure, when followed precisely, leads to the incorrect conclusion that the angular momentum of an accretion disk flows from the outer part to the inner part.
14631759
Hiding cusps in cores: kinematics of disc galaxies in triaxial dark matter haloes
We study the kinematics of gaseous discs in triaxial dark matter haloes using the closed-loop orbit solutions in non-axisymmetric potentials. The orbits are in general non-circular and, for a given triaxiality, their ellipticity depends on the ratio of escape to circular velocities, V 2 esc /V 2 c . This ratio increases steeply towards the centre for cold dark matter (CDM) halo density profiles, implying that even minor deviations from spherical symmetry may induce large deviations from circular orbits in the velocity field of a gaseous disc, especially near the centre. This result suggests that caution should be exercised when interpreting constraints on the presence of density cusps in the dark halo derived from the innermost velocity profile. Simulated long-slit rotation curves vary greatly in shape, depending primarily on the viewing angle of the disc and on its orientation relative to the principal axes of the potential. 'Solid-body' rotation curves - typically interpreted as a signature of a constant density core in the dark matter distribution - are often obtained when the slit samples velocities near the major axis of the closed-loop orbits. Triaxial potentials imprint specific symmetries in 2D velocity fields, generally inducing 'twists' in the isovelocity contours and antisymmetric patterns in opposite quadrants. We suggest that triaxial haloes may be responsible for the variety of shapes of long-slit rotation curves of low surface brightness (LSB) galaxies, as well as for the complex central kinematics of LSBs, which are sometimes ascribed to the presence of 'radial motions' in the gas. We argue that LSB rotation curves might be reconciled with the structure of CDM haloes once the effects of halo triaxiality on the dynamics of gaseous discs are properly taken into account.
119334547
THE STRUCTURAL EVOLUTION OF SUBSTRUCTURE
We investigate the evolution of substructure in cold dark matter (CDM) halos using N-body simulations of tidal stripping of substructure halos within a static host potential. We find that halos modeled following the Navarro, Frenk, & White (NFW) mass profile lose mass continuously because of tides from the massive host, leading to the total disruption of satellite halos with small tidal radii. Although mass is predominantly stripped from the outer regions, tidal heating also causes the halo to expand and the central density to decrease after each pericentric passage, when mass loss preferentially occurs. As a result, simple models based on the tidal-limit approximation underestimate significantly the tidal mass loss over several orbits. The equilibrium structure of stripped NFW halos depends mainly on the fraction of mass lost and can be expressed in terms of a simple correction to the original NFW profile. We apply these results to substructure in the Milky Way and conclude that the dark matter halos surrounding its dwarf spheroidal (dSph) satellites have circular velocity curves that peak well beyond the luminous radius at velocities significantly higher than expected from the stellar line-of-sight velocity dispersion. Our modeling suggests that the true tidal radii of dSphs lie well beyond the putative tidal cutoff observed in the surface brightness profile, suggesting that the latter are not really tidal in origin but rather features in the light profile of limited dynamical relevance. For Draco in particular, our modeling implies that its tidal radius is much larger than derived by Irwin & Hatzidimitriou, lending support to the interpretation of recent Sloan Digital Sky Survey data by Odenkirchen et al. Similarly, our model suggests that Carina’s halo has a peak circular velocity of order � 55 km s � 1 , which may help explain how this small galaxy has managed to retain enough gas to undergo several bursts of star formation. Our results imply a close correspondence between the most massive substructure halos expected in a CDM universe and the known satellites of the Milky Way and suggest that only substructure halos with peak circular velocities below 35 km s � 1 lack readily detectable luminous counterparts. Subject headings: cosmology: theory — dark matter — galaxies: evolution — galaxies: halos — galaxies: structure — methods: N-body simulations
18027030
Septum and kicker pulsers for the LNLS 500-MeV booster synchrotron
Brazilian National Synchrotron Light Laboratory (LNLS) has commissioned its new 500-MeV booster synchrotron injector. In this paper we present an overview of the septum and kicker pulse circuits now in operation. Half-sine wave septum current pulses range from 6.1 kA to 7.3 kA with widths around 80 /spl mu/s. Injection and extraction kicker circuits are capable of delivering currents up to 650 A and 1.2 kA, with fall and rise times consistent with the booster revolution period of 112 ns.