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The SLD Collaboration is now using new vextex detector (VXD3). The VXD3 is a significant improvement over the original SLD pixel vertex detector VXD2. The upgrade to VXD3 will significantly improve perfomance and open new, exciting possibilities for physics at SLD.
The VXD3 is placed
close to the e+ e- intersection point to improve the impact parameter resolution.
The system is composed of 3 barrels of charge couple detectors (CCDs),
a total of 96 CCDs which have 307 million pixels. These three barrels of
CCD's are capaple of tracking a particle through three points along its
path with a resolution of about 5 microns in all layers of CCDs. The three
cylindrical layers of CCD are placed at 28.0mm, 38.1mm, 48.3mm radii.
The CCDs of VXD3 are also longer resulting in increased solid angle coverage. Whereas VXD2 provided a 2-hit coverage only up to cosine of angle of collision (cos0) =0.75, the VXD3 provides 2-hit coverage up to cos0=0.85 and 3-hit coverage up to cos0=0.9.
The VXD3 will allow a measurement of the polarization-enhanced forward-backward asymetry for b- and c- quarks and improved precision in the measurement of the b- fraction in the hadronic Z decays, sufficient for testing radiative corrections in electroweak theory. The most exciting new possibility is the search for Bs- mixing -leading to a measurement of the mixing parameter xs.
This was based on VXD3: the SLD Vertex Detector Upgrade Based on a 307 MPixel CCD System, by J. E. Brau, University of Oregon.