18354661
Weak Lensing from Space. II. Dark Matter Mapping
We study the accuracy with which weak-lensing measurements could be made from a future space-based survey, predicting the subsequent precision of three-dimensional dark matter maps, projected two-dimensional dark matter maps, and mass-selected cluster catalogs. As a baseline, we use the instrumental specifications of the SuperNova/Acceleration Probe (SNAP) satellite. We first compute its sensitivity to weak lensing shear as a function of survey depth. Our predictions are based on detailed image simulations created using "shapelets," a complete and orthogonal parameterization of galaxy morphologies. We incorporate a realistic redshift distribution of source galaxies and calculate the average precision of photometric redshift recovery using the SNAP filter set to be Δz = 0.034. The high density of background galaxies resolved in a wide space-based survey allows projected dark matter maps with an rms sensitivity of 3% shear in 1 arcmin2 cells. This will be further improved using a proposed deep space-based survey, which will be able to detect isolated clusters using a three-dimensional lensing inversion technique with a 1 σ mass sensitivity of approximately 1013 M⊙ at z = 0.25. Weak-lensing measurements from space will thus be able to capture non-Gaussian features arising from gravitational instability and map out dark matter in the universe with unprecedented resolution.
17561360
Search for Invisible Or Lepton-Flavor-Violating Upsilon Decays in BaBar
Both invisible and lepton-flavor-violating Upsilon decays are unobservably rare in the Standard Model, but are each predicted to occur in several beyond-Standard-Model scenarios. We search for invisible, as well as for lepton-flavor-violating, Upsilon decays in a sample of 117 × 10 6
118956204
Observation of Gamma Rays from the Galactic Center with the MAGIC Telescope
Recently, the Galactic center has been reported to be a source of very high energy (VHE) gamma-rays by the CANGAROO, VERITAS, and HESS experiments. The energy spectra as measured by these experiments show substantial differences. In this Letter we present MAGIC observations of the Galactic center, resulting in the detection of a differential gamma-ray flux consistent with a steady, hard-slope power law, described as dN gamma/(dA dt dE) = (2.9 +/- 0.6) x 10(-12) (E/TeV)-2.2 +/- 0.2 cm(-2) s(-1) TeV-1. The gamma-ray source is centered at (R.A., decl.) p (17(h)45(m)20(s), -29 degrees 2'). This result confirms the previous measurements by the HESS experiment and indicates a steady source of TeV gamma-rays. We briefly describe the observational technique used and the procedure implemented for the data analysis, and we discuss the results in the perspective of different models proposed for the acceleration of the VHE gamma-rays.
119385567
FADC signal reconstruction for the MAGIC telescope
Until April 2007 the Major Atmospheric Gamma ray Imaging Cherenkov (MAGIC) telescope used a 300 MSamples/s flash analog-to-digital converter (FADC) system to sample the shaped photomultiplier tube (PMT) signals produced by the captured Cherenkov photons of air showers. Different algorithms to reconstruct the signal from the read-out samples (extractors) have been implemented and are described and compared. Criteria based on the obtained charge and time resolution/bias are defined and used to judge the different extractors, by applying them to calibration, cosmic and pedestal signals. The achievable charge and time resolution have been derived as functions of the number of incident photoelectrons. (C) 2008 Elsevier B.V. All rights reserved.