2761770
Jovian dust streams: A monitor of Io's volcanic plume activity
[1] Streams of high speed dust particles originate from Jupiter's moon Io. After release from Io, the particles collect electric charges in the Io plasma torus, gain energy from the co-rotating electric field of Jupiter's magnetosphere, and leave the Jovian system into interplanetary space with escape speeds over 200 km s−1. The Galileo spacecraft has continuously monitored the dust streams during 34 revolutions about Jupiter between 1996 and 2002. The observed dust fluxes exhibit large orbit-to-orbit variability due to systematic and stochastic changes. After removal of the systematic variations, the total dust emission rate of Io has been calculated. It varies between 10−3 and 10 kg s−1, and is typically in the range of 0.1 to 1 kg s−1. We compare the dust emission rate with other markers of volcanic activity on Io like large-area surface changes caused by volcanic deposits and sightings of volcanic plumes.
119408500
Observations of Electromagnetically Coupled Dust in the Jovian Magnetosphere
We report on dust measurements obtained during the seventh orbit of the Galileo spacecraft about Jupiter. The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by more than an order of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. In addition to the 5 and 10 h periodicities, a longer period which is compatible with Io's orbital period is evident in the dust impact rate. This feature indicates that Io most likely is the source of the dust streams. During a close (3,095 km altitude) flyby at Ganymede on 5 April 1997 an enhanced rate of dust impacts has been observed, which suggests that Ganymede is a source of ejecta particles. Within a distance of about 25 RJ(Jupiter radius, RJ= 71,492 km) from Jupiter impacts of micrometer-sized particles have been recorded which could be particles on bound orbits about Jupiter.
119344064
Dust Measurements in the Outer Solar System
Dust measurements in the outer solar system are reviewed. Only the plasma wave instrument on board Voyagers 1 and 2 recorded impacts in the Edgeworth-Kuiper belt (EKB). Pioneers 10 and 11 measured a constant dust flux of 10-micron-sized particles out to 20 AU. Dust detectors on board Ulysses and Galileo uniquely identified micron-sized interstellar grains passing through the planetary system. Impacts of interstellar dust grains onto big EKB objects generate at least about a ton per second of micron-sized secondaries that are dispersed by Poynting-Robertson effect and Lorentz force. We conclude that impacts of interstellar particles are also responsible for the loss of dust grains at the inner edge of the EKB. While new dust measurements in the EKB are in an early planning stage, several missions (Cassini and STARDUST) are en route to analyze interstellar dust in much more detail.
7572210
A dust cloud of Ganymede maintained by hypervelocity impacts of interplanetary micrometeoroids
Abstract A dust cloud of Ganymede has been detected by in situ measurements with the dust detector onboard the Galileo spacecraft. The dust grains have been sensed at altitudes below five Ganymede radii (Ganymede radius =2635 km ). Our analysis identifies the particles in the dust cloud surrounding Ganymede by their impact direction, impact velocity, and mass distribution and implies that they have been kicked up by hypervelocity impacts of micrometeoroids onto the satellite's surface. We calculate the radial density profile of the particles ejected from the satellite by interplanetary dust grains. We assume the yields, mass and velocity distributions of the ejecta obtained from laboratory impact experiments onto icy targets and consider the dynamics of the ejected grains in ballistic and escaping trajectories near Ganymede. The spatial dust density profile calculated with interplanetary particles as impactors is consistent with the profile derived from the Galileo measurements. The contribution of interstellar grains as projectiles is negligible. Dust measurements in the vicinities of satellites by spacecraft detectors are suggested as a beneficial tool to obtain more knowledge about the satellite surfaces, as well as dusty planetary rings maintained by satellites through the impact ejecta mechanism.
13912153
Analysis of the sensor characteristics of the Galileo dust detector with collimated Jovian dust stream particles
Abstract The Dust Detector System onboard Galileo records dust impacts in the Jupiter system. Impact events are classified into four quality classes. Class 3, our highest quality class, has always been noise-free and, therefore, contains only true dust impacts. Depending on the noise environment, Class 2 are dust impacts or noise. Within 20RJ from Jupiter (Jupiter radius, RJ = 71,492 km) Class 2 shows clear indications for contamination by noise. We analyse the dust data from Galileos prime Jupiter mission (1996 and 1997), separate dust impacts from noise events and derive a complete denoised set of Galileo dust data (Classes 2 and 3). Collimated streams of nanometer-sized dust particles which have been detected throughout the Jovian system (Grun et al., 1998, J. Geophys. Res., 103, 20,011–20,022) are used to analyse the sensitive area and the field of view of the dust detector itself. The sensitive area for stream particles which trigger Class 3 events is 110±37 cm2. This is almost a factor of ten smaller than the total sensitive area for Class 2 impacts (1000 cm2). Correspondingly, the field of view of the detector for Class 3 stream particles is reduced from 140 to 96°. The magnetometer boom and other instruments on board Galileo cause a significant shadowing of the field of view of the dust sensor. Our analysis is supplementary to ground calibrations of the dust instrument because the low masses and high speeds of the stream particles could not be achieved in the laboratory. Our new results have important consequences for the analysis of dust in the Jupiter system.
38484024
Precision measurements of the lambda(+)(c) and D0 lifetimes.
We report new precision measurements of the lifetimes of the Lambda(+)(c) and D0 from SELEX, the charm hadroproduction experiment at Fermilab. Based upon 1630 Lambda(+)(c) and 10 210 D0 decays we observe lifetimes of tau[Lambda(+)(c)] = 198.1+/-7.0+/-5.6 fs and tau[D0] = 407.9+/-6.0+/-4.3 fs.
67816405
Study of noise and spectroscopic performance of DEPMOSFET matrix prototypes for XEUS
Abstract The current generation of DEPMOSFET-based Active Pixel Sensor (APS) matrix devices has been developed to cope with the challenging requirements of the XEUS Wide Field Imager. The devices turned out to be a promising new imager concept for a variety of X-ray imaging applications. The devices combine excellent energy resolution, high-speed readout and low power consumption with the attractive feature of random accessibility of pixels. Sensor prototypes, built for row-wise readout, with 64 × 64 pixels with a size of 75 × 75 μ m 2 each have been produced at the MPI semiconductor laboratory in Munich, and their performance has been studied in detail. A spectroscopic resolution of 128 eV has been measured, the readout noise is as low as 3.5 e - ENC. Here, measurements of the dependence of readout noise and spectroscopic resolution on the device temperature are presented.
109931424
Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H --> gamma-gamma, H --> ZZ* --> 4 leptons and H --> WW --> 2 leptons + 2 neutrinos. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of about 25/fb. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson.
209521027
Measurement of upsilon production in 7 TeV pp collisions at ATLAS
Using 1.8  fb-1 of pp collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the Large Hadron Collider, we present measurements of the production cross sections of Υ(1S,2S,3S) mesons. Υ mesons are reconstructed using the dimuon decay mode. Total production cross sections for pT<70  GeV and in the rapidity interval |yΥ|<2.25 are measured to be, 8.01±0.02±0.36±0.31  nb, 2.05±0.01±0.12±0.08  nb, and 0.92±0.01±0.07±0.04  nb, respectively, with uncertainties separated into statistical, systematic, and luminosity measurement effects. In addition, differential cross section times dimuon branching fractions for Υ(1S), Υ(2S), and Υ(3S) as a function of Υ transverse momentum pT and rapidity are presented. These cross sections are obtained assuming unpolarized production. If the production polarization is fully transverse or longitudinal with no azimuthal dependence in the helicity frame, the cross section may vary by approximately ±20%. If a nontrivial azimuthal dependence is considered, integrated cross sections may be significantly enhanced by a factor of 2 or more. We compare our results to several theoretical models of Υ meson production, finding that none provide an accurate description of our data over the full range of Υ transverse momenta accessible with this data set.