6,902 research outputs found
A CCD vertex deetctor for a high-energy linear e+e- collider
I present a summary of the experience with CCD-based vertex detectors at the
SLD experiment at SLAC, and discuss their advantages for use at a future
high-energy e+e- collider. The extensive R+D programme to improve further the
vertexing capabilities of CCD detectors is also outlined.Comment: 14 pages latex including 4 embedded ps files, to appear in
Proceedings Vertex99 Worksho
Optical spectroscopy of a brown dwarf candidate
We have used the Low-Resolution Imaging Spectrograph on the Keck II telescope
to observe the brown dwarf candidate D04 (Hawkins et al, 1998). The spectrum
matches that of a spectral-type M7 dwarf, implying a photospheric temperature
of K. This is consistent with the available (R-I) and (I-K)
colours. If the parallax measured by Hawkins et al is correct, then the
implication is that D04 has a radius of , or one-third that
of Jupiter. This contradicts the predictions made by current stellar models
that electron degeneracy leads to nearly constant radii for stars and brown
dwarfs at masses below 0.1 M. We suggest that an equally valid
interpretation of the data is that D04 is a VB8 analogue at a distance of
parsecs.Comment: to appear in MNRAS, pink pages; 6 pages with 1 jpg, 1 postscript
figur
Summary of Discussion Question 4: Energy Expandability of a Linear Collider
We report on Discussion Question 4, in Sub-group 1 (`TeV-class') of the
Snowmass Working Group E3: `Experimental Approaches: Linear Colliders', which
addresses the energy expandability of a linear collider. We first synthesize
discussions of the energy reach of the hardware of the 500 GeV designs for
TESLA and NLC/JLC. Next, we review plans for increasing the energy to 800-1000
GeV. We then look at options for expanding the energies to 1500 GeV and sketch
the two-beam accelerator approach to achieving multi-TeV energies.Comment: Presented at Snowmass 2001 (6 pages, 2 figures
Probing the galactic halo with ROSAT
We discuss the current status of ROSAT shadowing observations designed to search for emission from million degree gas in the halo of the Milky Way galaxy. Preliminary results indicate that million degree halo gas is observed in the 1/4 keV band in some directions, most notably toward the Draco cloud at (l,b) = (92 deg, +38 deg), but that the halo emission is patchy and highly anisotropic. Our current understanding of this halo emission is based on a small handful of observations which have been analyzed to date. Many more observations are currently being analyzed or are scheduled for observation within the next year, and we expect our understanding of this component of the galactic halo to improve dramatically in the near future
- …