101 research outputs found
New Results From BABAR
The BABAR experiment at the PEP-II asymmetric B factory at SLAC has collected
a large sample of data at the resonance. I will summarize
BABAR's new results on CP violation, B mixing and lifetimes, and a selection of
rare B decays. In particular, I will describe in detail the measurement of the
CP violating parameter ; BABAR has observed CP violation in the
neutral B system finding .Comment: 20 pages, 27 postscript figues, submitted to the 21st Physics In
Collision Conference (PIC 2001
The Third Gravitational Lensing Accuracy Testing (GREAT3) Challenge Handbook
The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third
in a series of image analysis challenges, with a goal of testing and
facilitating the development of methods for analyzing astronomical images that
will be used to measure weak gravitational lensing. This measurement requires
extremely precise estimation of very small galaxy shape distortions, in the
presence of far larger intrinsic galaxy shapes and distortions due to the
blurring kernel caused by the atmosphere, telescope optics, and instrumental
effects. The GREAT3 challenge is posed to the astronomy, machine learning, and
statistics communities, and includes tests of three specific effects that are
of immediate relevance to upcoming weak lensing surveys, two of which have
never been tested in a community challenge before. These effects include
realistically complex galaxy models based on high-resolution imaging from
space; spatially varying, physically-motivated blurring kernel; and combination
of multiple different exposures. To facilitate entry by people new to the
field, and for use as a diagnostic tool, the simulation software for the
challenge is publicly available, though the exact parameters used for the
challenge are blinded. Sample scripts to analyze the challenge data using
existing methods will also be provided. See http://great3challenge.info and
http://great3.projects.phys.ucl.ac.uk/leaderboard/ for more information.Comment: 30 pages, 13 figures, submitted for publication, with minor edits
(v2) to address comments from the anonymous referee. Simulated data are
available for download and participants can find more information at
http://great3.projects.phys.ucl.ac.uk/leaderboard
Photometry, Centroid and Point-Spread Function Measurements in the LSST Camera Focal Plane Using Artificial Stars
The Vera C. Rubin Observatory's LSST Camera pixel response has been
characterized using laboratory measurements with a grid of artificial stars. We
quantify the contributions to photometry, centroid, point-spread function size,
and shape measurement errors due to small anomalies in the LSSTCam CCDs. The
main sources of those anomalies are quantum efficiency variations and pixel
area variations induced by the amplifier segmentation boundaries and
"tree-rings" -- circular variations in silicon doping concentration. We studied
the effects using artificial stars projected on the sensors and find that the
resulting measurement uncertainties pass the ten-year LSST survey science
requirements. In addition, we verify that the tree-ring effects can be
corrected using flat-field images if needed, because the astronomic shifts and
shape measurement errors they induce correlate well with the flat-field signal.
Nevertheless, further sensor anomaly studies with on-sky data should probe
possible temporal and wavelength-dependent effects.Comment: Submitted to PAS
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