Improvements in CLEO tracking with the SVX

CLEO has now been taking data with the silicon vertex detector (SV) for about four months. During that time, we have made progress with the alignment of the detector, and with using the SV information to improve our tracking.

First hadronic event

Here is a sample hadronic event, most likely the decay of a pair of tau leptons. All of the tracks in the VD and DR also go through hits in the SV; in fact, the positions of these tracks are strongly constrained by the SV.

Another hadronic event

The tracking is also quite successful in busier events, like the one above. There is still plenty of noise in the detector, but the spatial resolution of the SV is good enough to allow us to associate the correct tracks with hits. The track in the lower left quadrant does not go through any SV hits; it appears to be a particle that scattered off the inner wall of the VD.

Kshort event

This event is interesting because the two tracks in the lower right quadrant do overlap. They form a vertex, and if we assume that both tracks were made by pions, the resulting vertex is consistent with the decay of a Ks, which traveled eight millimeters during its short lifetime.

Since "vertex" is the middle name of the silicon vertex detector, our goal is to use this device to find such vertices on a regular basis, and to use them to enhance our understanding of the physics of heavy mesons and leptons.

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