SVT: an online silicon vertex tracker for the CDF upgrade Page: 3 of 6

CDF/PUB/TRIGGER/PUBLIC/4246

SVT: an online Silicon Vertex Tracker for the CDF upgrade
A.Bardi0, S.Belforte, J.Berryhill", A.Cerri, A.G.Clarkb, R.Culbertson", M.Dell'Orso,
S.Donati0, J.Dusatko", H.J.Frisch", S.Galeotti, P.Giannetti, A.Legerb, E.Meschi,
F.Morsani0, T.Nakaya", G.Punzi, L.Ristori, H.Sanders", M.Shochet", T.Speerb, F.Spinella,
P.Wilson", X.Wub, A.M.Zanettid.
a University of Chicago - U.S.A.
b University of Geneve - Switzerland
University, Scuola Normale Superiore and INFN Pisa - Italy
dINFN Trieste - Italy
The SVT is an online tracker for the CDF upgrade which will reconstruct 2D tracks using
information from the Silicon VerteX detector (SVXII) and Central Outer Tracker (COT).
The precision measurement of the track impact parameter will then be used to select and
record large samples of B hadrons. We discuss the overall architecture, algorithms, and
hardware implementation of the system
1 Introduction
The SVT will work in the level 2 of the CDF trigger chain, to refine the level 1 tracking
information from the eXtra Fast Tracker (XFT), which uses data from the central drift chamber
COT. It will combine XFT tracks with hit coordinates from the SVXII.
The level 2 latency time is about 20 ps, therefore the design of the SVT has concentrated on
parallelizing the various tasks, from the reconstruction of the hit coordinates from the single
strip pulse heights to the pattern recognition and final precision track fitting (Fig.1). The result
is a data driven architecture in which many functions overlap in the internal processor pipeline,
and which comprises several different modules, built on 9U Eurocard boards with VMEbus
implementation for diagnostic and control. The SVT specifications require 30 MHz operation
for each module and an asynchronous data transfer rate of 630 Mbit/s on custom data paths.
2 Tracking Strategy
In a typical two-jet event at CDFII about 60 tracks will traverse the SVXII, and about 6,000
strips will have a significant pulse height (we assume a 5 % occupancy dominated by noise).
SVT will receive sparsified and digitized pulse heights from the front end via an optical link.
After pedestal subtraction, the Hit Finder board (HF) finds hits and calculates the charge
center-of-gravity.
Hits from HF and track parameters from the XFT are sent simultaneously to the Associative
Memory bank (AM) and the Hit Buffer (HB). The COT track candidates found by XFT (about
3 per event on the average) are then matched to SVXII hits in the AM, which performs the
first pattern recognition with limited resolution (the detector is subdivided into superstrips
1 Published proceedings 7th Pisa meeting on Advanced Detectors, La Biodola, I.
d'Elba (Italy), May 25-31, 1997 - presented by E.Meschi

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Bardi, A.; Belforte, S. & Berryhill, J. SVT: an online silicon vertex tracker for the CDF upgrade, article, July 1, 1997; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc690535/m1/3/ocr/: accessed December 11, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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