118861611
Observation of inclusive. omega. production at large transverse momentum
We have observed the production of ..omega.. mesons at large transverse momentum produced in 200-GeV/c pBe interactions. The ratio of inclusive production of ..omega.. to ..pi../sup 0/ at transverse momenta above 2.2 GeV/c is 0.44 +- 0.08 near x=0. The upper limit for eta' to eta production is <1.4 in the same kinematic region.
115852024
Measurement of the quantum efficiency of TMAE and TEA from threshold to 120 nm
Several existing and planned high energy physics experiments incorporate detectors which use either TMAE (tetrakis-dimethylaminoethylene) or TEA (triethylamine) as their photosensitive agent. Understanding the operation of these devices requires knowledge of the absolute photoionization quantum efficiencies and absorption lengths of TMAE and TEA. In an experiment performed at the National Synchrotron Light source at Brookhaven National Laboratory, we have measured these parameters from 120 nm to 280 nm. The quantum efficiencies were normalized to the known photoionization yields of benzene and cis-2-butene. The results of these measurements and details of the experiment are presented in this paper.
18850797
Detection of Diffuse Interstellar Bands in the z=0.5 Damped Lyman alpha system towards AO 0235+164
We report the first detection of the 5705 and 5780 A Diffuse Interstellar Bands (DIBs) in a moderate redshift Damped Lyman alpha (DLA) system. We measure a rest frame equivalent width of 63.2 +- 8.7 mA for the 5705 and 216+-9 mA for the 5780 A feature in the z_abs 0.524 DLA towards AO 0235+164 and derive limits for the equivalent widths of the bands at 5797, 6284, and 6613 A. The equivalent width of the 5780 band is lower than would be expected based on the Galactic correlation of DIB strength with N(HI), but is in good agreement with the correlation with E(B-V). The relative strengths of the 5780 and 6284 A DIBs are inconsistent with all Galactic and extragalactic sightlines, except one Small Magellanic Cloud wing sightline towards Sk 143. However, the relative strengths of the 5705 and 5780 A DIBs are consistent with the Galactic relation, indicating that the relative strengths of these bands may be less sensitive to environment or that they may be associated with a similar carrier. The detection of DIBs at z~0.5 demonstrates that the organic compounds usually assumed to be the band carriers were already present in the universe some five gigayears ago.
17422475
Probing the Nature of the G1 Clump Stellar Overdensity in the Outskirts of M31
We present deep Hubble Space Telescope ACS observations of the G1 clump, a distinct stellar overdensity lying at similar to 30 kpc along the southwestern major axis of M31, close to the G1 globular cluster ( from the work of Ferguson and coworkers). Our well-populated color-magnitude diagram reaches similar to 7 mag below the red giant branch tip with 90% completeness, and allows the detection of various morphological features that can be used to derive detailed constraints on the age and metallicity of the constituent stellar population. We find that the color-magnitude diagram is best described spread in metallicity is constrained to be P = 0.5 dex. The star formation rate in this region has declined over time, with the bulk of the stellar mass having formed > 6 Gyr ago. Nonetheless, a nonnegligible mass fraction (approximate to 10%) of the population has formed in the last 2 Gyr. We discuss the nature of the G1 clump in light of these new stellar population constraints and argue that the combination of stellar content and physical size make it unlikely that the structure is the remnant of an accreted dwarf galaxy. Instead, the strong similarity between the stellar content of the G1 clump and that of the M31 outer disk suggests that the substructure is a fragment of the outer disk, perhaps torn off from the main body during a past accretion/merger event; this interpretation is consistent with extant kinematical data. If this interpretation is correct, our analysis of the stellar content provides further evidence that the outskirts of large disk galaxies have been in place for a significant time. (Less)
16108826
Validation of spallation neutron production and propagation within Geant4
Using simulations to understand backgrounds from muon-induced neutrons is important in designing next-generation low-background underground experiments. Validation of relevant physics within the Geant4 simulation package has been completed by comparing to data from two recent experiments. Verification focused on the production and propagation of neutrons at energies important to underground experiments. Discrepancies were observed between experimental data and the simulation. Techniques were explored to correct for these discrepancies.
118751982
The GLAST LAT Silicon Strip Tracker Converter
The Tracker subsystem of the Large Area Telescope (LAT) science instrument of the Gamma‐ray Large Area Space Telescope (GLAST) mission has been completed and tested. It is the central detector subsystem of the LAT and serves both to convert an incident gamma‐ray into an electron‐positron pair and to track the pair in order to measure the gamma‐ray direction. It also provides the principal trigger for the LAT. The Tracker uses silicon strip detectors, read out by custom electronics, to detect charged particles. The detectors and electronics are packaged, along with tungsten converter foils, in 16 modular, high‐precision carbon‐composite structures. The test program has demonstrated that the system meets or surpasses all of its performance specifications as well as environmental requirements.
62900586
The GLAST large area telescope instrument
Abstract The LAT instrument on the Gamma-ray Large Area Space Telescope (GLAST) project is a gamma-ray pair-conversion telescope designed to improve upon the sensitivity of the Compton Gamma-Ray Observatory EGRET instrument by at least a factor of 30. The LAT design is based upon a silicon-strip tracker/converter, a CsI calorimeter, and a plastic-scintillator anticoincidence shield. The project is approaching its critical design review and is scheduled for launch in 2006. This talk gives an overview of the LAT science objectives, the LAT design, and the status of the engineering effort and instrument production plans.